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In the present study, a novel approach for mid-infrared (IR)-based prediction of bovine milk fatty acid composition is introduced. A rapid, solvent-free, two-step centrifugation method was applied in order to obtain representative milk fat fractions. IR spectra of pure milk lipids were recorded with attenuated total reflection Fourier-transform infrared (ATR-FT-IR) spectroscopy. Comparison to the IR transmission spectra of whole milk revealed a higher amount of significant spectral information for fatty acid analysis. Partial least squares (PLS) regression models were calculated to relate the IR spectra to gas chromatography/mass spectrometry (GC/MS) reference values, providing particularly good predictions for fatty acid sum parameters as well as for the following individual fatty acids: C10:0 (R2 P = 0.99), C12:0 (R2 P = 0.97), C14:0 (R2 P = 0.88), C16:0 (R2 P = 0.81), C18:0 (R2 P = 0.93), and C18:1cis (R2 P = 0.95). The IR wavenumber ranges for the individual regression models were optimized and validated by calculation of the PLS selectivity ratio. Based on a set of 45 milk samples, the obtained PLS figures of merit are significantly better than those reported in literature using whole milk transmission spectra and larger datasets. In this context, direct IR measurement of the milk fat fraction inherently eliminates covariation structures between fatty acids and total fat content, which poses a common problem in IR-based milk fat profiling. The combination of solvent-free lipid separation and ATR-FT-IR spectroscopy represents a novel approach for fast fatty acid prediction, with the potential for high-throughput application in routine lab operation.
Christopher Akhgar; Vanessa Nürnberger; Marlene Nadvornik; Margit Velik; Andreas Schwaighofer; Erwin Rosenberg; Bernhard Lendl. Fatty Acid Prediction in Bovine Milk by Attenuated Total Reflection Infrared Spectroscopy after Solvent-Free Lipid Separation. Foods 2021, 10, 1054 .
AMA StyleChristopher Akhgar, Vanessa Nürnberger, Marlene Nadvornik, Margit Velik, Andreas Schwaighofer, Erwin Rosenberg, Bernhard Lendl. Fatty Acid Prediction in Bovine Milk by Attenuated Total Reflection Infrared Spectroscopy after Solvent-Free Lipid Separation. Foods. 2021; 10 (5):1054.
Chicago/Turabian StyleChristopher Akhgar; Vanessa Nürnberger; Marlene Nadvornik; Margit Velik; Andreas Schwaighofer; Erwin Rosenberg; Bernhard Lendl. 2021. "Fatty Acid Prediction in Bovine Milk by Attenuated Total Reflection Infrared Spectroscopy after Solvent-Free Lipid Separation." Foods 10, no. 5: 1054.
Many of graphene’s remarkable properties arise from its linear dispersion of the electronic states, forming a Dirac cone at the K points of the Brillouin zone. Silicene, the 2D allotrope of silicon, is also predicted to show a similar electronic band structure, with the addition of a tunable bandgap, induced by spin–orbit coupling. Because of these outstanding electronic properties, silicene is considered as a promising building block for next-generation electronic devices. Recently, it has been shown that silicene grown on Au(111) still possesses a Dirac cone, despite the interaction with the substrate. Here, to fully characterize the structure of this 2D material, we investigate the vibrational spectrum of a monolayer silicene grown on Au(111) by polarized Raman spectroscopy. To enable a detailed ex situ investigation, we passivated the silicene on Au(111) by encapsulating it under few layers hBN or graphene flakes. The observed spectrum is characterized by vibrational modes that are strongly red-shifted with respect to the ones expected for freestanding silicene. By comparing low-energy electron diffraction (LEED) patterns and Raman results with first-principles calculations, we show that the vibrational modes indicate a highly (>7%) biaxially strained silicene phase.
Daniele Nazzari; Jakob Genser; Viktoria Ritter; Ole Bethge; Emmerich Bertagnolli; Georg Ramer; Bernhard Lendl; Kenji Watanabe; Takashi Taniguchi; Riccardo Rurali; Miroslav Kolíbal; Alois Lugstein. Highly Biaxially Strained Silicene on Au(111). The Journal of Physical Chemistry C 2021, 125, 9973 -9980.
AMA StyleDaniele Nazzari, Jakob Genser, Viktoria Ritter, Ole Bethge, Emmerich Bertagnolli, Georg Ramer, Bernhard Lendl, Kenji Watanabe, Takashi Taniguchi, Riccardo Rurali, Miroslav Kolíbal, Alois Lugstein. Highly Biaxially Strained Silicene on Au(111). The Journal of Physical Chemistry C. 2021; 125 (18):9973-9980.
Chicago/Turabian StyleDaniele Nazzari; Jakob Genser; Viktoria Ritter; Ole Bethge; Emmerich Bertagnolli; Georg Ramer; Bernhard Lendl; Kenji Watanabe; Takashi Taniguchi; Riccardo Rurali; Miroslav Kolíbal; Alois Lugstein. 2021. "Highly Biaxially Strained Silicene on Au(111)." The Journal of Physical Chemistry C 125, no. 18: 9973-9980.
A thermostabilized aluminium acoustic trap combined with attenuated total reflection infrared spectroscopy used to perform ultrasound-assisted E. coli detection.
Stephan Freitag; Bettina Baumgartner; Stefan Radel; Andreas Schwaighofer; Antonio Varriale; Angela Pennacchio; Sabato D'Auria; Bernhard Lendl. A thermoelectrically stabilized aluminium acoustic trap combined with attenuated total reflection infrared spectroscopy for detection of Escherichia coli in water. Lab on a Chip 2021, 21, 1811 -1819.
AMA StyleStephan Freitag, Bettina Baumgartner, Stefan Radel, Andreas Schwaighofer, Antonio Varriale, Angela Pennacchio, Sabato D'Auria, Bernhard Lendl. A thermoelectrically stabilized aluminium acoustic trap combined with attenuated total reflection infrared spectroscopy for detection of Escherichia coli in water. Lab on a Chip. 2021; 21 (9):1811-1819.
Chicago/Turabian StyleStephan Freitag; Bettina Baumgartner; Stefan Radel; Andreas Schwaighofer; Antonio Varriale; Angela Pennacchio; Sabato D'Auria; Bernhard Lendl. 2021. "A thermoelectrically stabilized aluminium acoustic trap combined with attenuated total reflection infrared spectroscopy for detection of Escherichia coli in water." Lab on a Chip 21, no. 9: 1811-1819.
Laser-based infrared (IR) spectroscopy is an emerging key technology for the analysis of solutes and for real-time reaction monitoring in liquids. Larger applicable pathlengths compared to the traditional gold standard Fourier transform IR (FTIR) spectroscopy enable robust measurements of analytes in a strongly absorbing matrix such as water. Recent advancements in laser development also provide large accessible spectral coverage thus overcoming an inherent drawback of laser-based IR spectroscopy. In this work, we benchmark a commercial room temperature operated broadband external cavity-quantum cascade laser (EC-QCL)-IR spectrometer with a spectral coverage of 400 cm−1 against FTIR spectroscopy and showcase its application for measuring the secondary structure of proteins in water, and for monitoring the lipase-catalyzed saponification of triacetin. Regarding the obtained limit of detection (LOD), the laser-based spectrometer compared well to a research-grade FTIR spectrometer employing a liquid nitrogen cooled detector. With respect to a routine FTIR spectrometer equipped with a room temperature operated pyroelectric detector, a 15-fold increase in LOD was obtained in the spectral range of 1600–1700 cm−1. Characteristic spectral features in the amide I and amide II region of three representative proteins with different secondary structures could be measured at concentrations as low as 0.25 mg mL−1. Enzymatic hydrolysis of triacetin by lipase was monitored, demonstrating the advantage of a broad spectral coverage for following complex chemical reactions. The obtained results in combination with the portability and small footprint of the employed spectrometer opens a wide range of future applications in protein analysis and industrial process control, which cannot be readily met by FTIR spectroscopy without recurring to liquid nitrogen cooled detectors.
Andreas Schwaighofer; Christopher K. Akhgar; Bernhard Lendl. Broadband laser-based mid-IR spectroscopy for analysis of proteins and monitoring of enzyme activity. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2021, 253, 119563 .
AMA StyleAndreas Schwaighofer, Christopher K. Akhgar, Bernhard Lendl. Broadband laser-based mid-IR spectroscopy for analysis of proteins and monitoring of enzyme activity. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 2021; 253 ():119563.
Chicago/Turabian StyleAndreas Schwaighofer; Christopher K. Akhgar; Bernhard Lendl. 2021. "Broadband laser-based mid-IR spectroscopy for analysis of proteins and monitoring of enzyme activity." Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 253, no. : 119563.
We report on a comparison between two optical detection techniques, one based on a Quartz-Enhanced Photoacoustic Spectroscopy (QEPAS) detection module, where a quartz tuning fork is acoustically coupled with a pair of millimeter-sized resonator tubes; and the other one based on a Photothermal Spectroscopy (PTS) module where a Fabry-Perot interferometer acts as transducer to probe refractive index variations. When resonant optical absorption of modulated light occurs in a gas sample, QEPAS directly detects acoustic waves while PTS probes refractive index variations caused by local heating. Compact QEPAS and PTS detection modules were realized and integrated in a gas sensor system for detection of carbon monoxide (CO), targeting the fundamental band at 4.6 μm by using a distributed-feedback quantum cascade laser. Performance was compared and ultimate detection limits up to ∼ 6 part-per-billion (ppb) and ∼15 ppb were reached for QEPAS and the PTS module, respectively, using 100 s integration time and 40 mW of laser power.
Davide Pinto; Harald Moser; Johannes P. Waclawek; Stefano Dello Russo; Pietro Patimisco; Vincenzo Spagnolo; Bernhard Lendl. Parts-per-billion detection of carbon monoxide: A comparison between quartz-enhanced photoacoustic and photothermal spectroscopy. Photoacoustics 2021, 22, 100244 .
AMA StyleDavide Pinto, Harald Moser, Johannes P. Waclawek, Stefano Dello Russo, Pietro Patimisco, Vincenzo Spagnolo, Bernhard Lendl. Parts-per-billion detection of carbon monoxide: A comparison between quartz-enhanced photoacoustic and photothermal spectroscopy. Photoacoustics. 2021; 22 ():100244.
Chicago/Turabian StyleDavide Pinto; Harald Moser; Johannes P. Waclawek; Stefano Dello Russo; Pietro Patimisco; Vincenzo Spagnolo; Bernhard Lendl. 2021. "Parts-per-billion detection of carbon monoxide: A comparison between quartz-enhanced photoacoustic and photothermal spectroscopy." Photoacoustics 22, no. : 100244.
In this work, we introduce polarimetric balanced detection as a new attenuated total reflection (ATR) infrared (IR) sensing scheme, leveraging unequal effective thicknesses achieved with laser light of different polarizations. We combined a monolithic widely tunable Vernier quantum cascade laser (QCL-XT) and a multibounce ATR IR spectroscopy setup for analysis of liquids in a process analytical setting. Polarimetric balanced detection enables simultaneous recording of background and sample spectra, significantly reducing long-term drifts. The root-mean-square noise could be improved by a factor of 10 in a long-term experiment, compared to conventional absorbance measurements obtained via the single-ended optical channel. The sensing performance of the device was further evaluated by on-site measurements of ethanol in water, leading to an improved limit of detection (LOD) achieved with polarimetric balanced detection. Sequential injection analysis was employed for automated injection of samples into a custom-built ATR flow cell mounted above a zinc sulfide multibounce ATR element. The QCL-XT posed to be suitable for mid-IR-based sensing in liquids due to its wide tunability. Polarimetric balanced detection proved to enhance the robustness and long-term stability of the sensing device, along with improving the LOD by a factor of 5. This demonstrates the potential for new polarimetric QCL-based ATR mid-IR sensing schemes for in-field measurements or process monitoring usually prone to a multitude of interferences.
Stephan Freitag; Matthias Baer; Laura Buntzoll; Georg Ramer; Andreas Schwaighofer; Bernhard Schmauss; Bernhard Lendl. Polarimetric Balanced Detection: Background-Free Mid-IR Evanescent Field Laser Spectroscopy for Low-Noise, Long-term Stable Chemical Sensing. ACS Sensors 2020, 6, 35 -42.
AMA StyleStephan Freitag, Matthias Baer, Laura Buntzoll, Georg Ramer, Andreas Schwaighofer, Bernhard Schmauss, Bernhard Lendl. Polarimetric Balanced Detection: Background-Free Mid-IR Evanescent Field Laser Spectroscopy for Low-Noise, Long-term Stable Chemical Sensing. ACS Sensors. 2020; 6 (1):35-42.
Chicago/Turabian StyleStephan Freitag; Matthias Baer; Laura Buntzoll; Georg Ramer; Andreas Schwaighofer; Bernhard Schmauss; Bernhard Lendl. 2020. "Polarimetric Balanced Detection: Background-Free Mid-IR Evanescent Field Laser Spectroscopy for Low-Noise, Long-term Stable Chemical Sensing." ACS Sensors 6, no. 1: 35-42.
Determination of the intracellular location of proteins is one of the fundamental tasks of microbiology. Conventionally, label-based microscopy and super-resolution techniques are employed. In this work, we demonstrate a new technique that can determine intracellular protein distribution at nanometer spatial resolution. This method combines nanoscale spatial resolution chemical imaging using the photothermal-induced resonance (PTIR) technique with multivariate modeling to reveal the intracellular distribution of cell components. Here, we demonstrate its viability by imaging the distribution of major cellulases and xylanases in Trichoderma reesei using the colocation of a fluorescent label (enhanced yellow fluorescence protein, EYFP) with the target enzymes to calibrate the chemometric model. The obtained partial least squares model successfully shows the distribution of these proteins inside the cell and opens the door for further studies on protein secretion mechanisms using PTIR.
A. Catarina V. D. Dos Santos; Rosa Heydenreich; Christian Derntl; Astrid R. Mach-Aigner; Robert L. Mach; Georg Ramer; Bernhard Lendl. Nanoscale Infrared Spectroscopy and Chemometrics Enable Detection of Intracellular Protein Distribution. Analytical Chemistry 2020, 92, 15719 -15725.
AMA StyleA. Catarina V. D. Dos Santos, Rosa Heydenreich, Christian Derntl, Astrid R. Mach-Aigner, Robert L. Mach, Georg Ramer, Bernhard Lendl. Nanoscale Infrared Spectroscopy and Chemometrics Enable Detection of Intracellular Protein Distribution. Analytical Chemistry. 2020; 92 (24):15719-15725.
Chicago/Turabian StyleA. Catarina V. D. Dos Santos; Rosa Heydenreich; Christian Derntl; Astrid R. Mach-Aigner; Robert L. Mach; Georg Ramer; Bernhard Lendl. 2020. "Nanoscale Infrared Spectroscopy and Chemometrics Enable Detection of Intracellular Protein Distribution." Analytical Chemistry 92, no. 24: 15719-15725.
The variable configuration of Raman spectroscopic platforms is one of the major obstacles in establishing Raman spectroscopy as a valuable physicochemical method within real-world scenarios such as clinical diagnostics. For such real world applications like diagnostic classification, the models should ideally be usable to predict data from different setups. Whether it is done by training a rugged model with data from many setups or by a primary-replica strategy where models are developed on a ‘primary’ setup and the test data are generated on ‘replicate’ setups, this is only possible if the Raman spectra from different setups are consistent, reproducible, and comparable. However, Raman spectra can be highly sensitive to the measurement conditions, and they change from setup to setup even if the same samples are measured. Although increasingly recognized as an issue, the dependence of the Raman spectra on the instrumental configuration is far from being fully understood and great effort is needed to address the resulting spectral variations and to correct for them. To make the severity of the situation clear, we present a round robin experiment investigating the comparability of 35 Raman spectroscopic devices with different configurations in 15 institutes within seven European countries from the COST (European Cooperation in Science and Technology) action Raman4clinics. The experiment was developed in a fashion that allows various instrumental configurations ranging from highly confocal setups to fibre-optic based systems with different excitation wavelengths. We illustrate the spectral variations caused by the instrumental configurations from the perspectives of peak shifts, intensity variations, peak widths, and noise levels. We conclude this contribution with recommendations that may help to improve the inter-laboratory studies.
Shuxia Guo; Claudia Beleites; Ute Neugebauer; Sara Abalde-Cela; Nils Kristian Afseth; Fatima Alsamad; Suresh Anand; Cuauhtemoc Araujo-Andrade; Sonja Aškrabić; Ertug Avci; Monica Baia; Malgorzata Baranska; Enrico Baria; Luis A. E. Batista de Carvalho; Philippe de Bettignies; Alois Bonifacio; Franck Bonnier; Eva Maria Brauchle; Hugh J. Byrne; Igor Chourpa; Riccardo Cicchi; Frederic Cuisinier; Mustafa Culha; Marcel Dahms; Catalina David; Ludovic Duponchel; Shiyamala Duraipandian; Samir F. El-Mashtoly; David I. Ellis; Gauthier Eppe; Guillaume Falgayrac; Ozren Gamulin; Benjamin Gardner; Peter Gardner; Klaus Gerwert; Evangelos J. Giamarellos-Bourboulis; Sveinbjorn Gizurarson; Marcin Gnyba; Royston Goodacre; Patrick Grysan; Orlando Guntinas-Lichius; Helga Helgadottir; Vlasta Mohaček Grošev; Catherine Kendall; Roman Kiselev; Micha Kölbach; Christoph Krafft; Sivashankar Krishnamoorthy; Patrick Kubryck; Bernhard Lendl; Pablo Loza-Alvarez; Fiona M. Lyng; Susanne Machill; Cedric Malherbe; Monica Marro; Maria Paula M. Marques; Ewelina Matuszyk; Carlo Francesco Morasso; Myriam Moreau; Howbeer Muhamadali; Valentina Mussi; Ioan Notingher; Marta Z. Pacia; Francesco S. Pavone; Guillaume Penel; Dennis Petersen; Olivier Piot; Julietta V. Rau; Marc Richter; Maria Krystyna Rybarczyk; Hamideh Salehi; Katja Schenke-Layland; Sebastian Schlücker; Markus Schosserer; Karin Schütze; Valter Sergo; Faris Sinjab; Janusz Smulko; Ganesh D. Sockalingum; Clara Stiebing; Nick Stone; Valérie Untereiner; Renzo Vanna; Karin Wieland; Jürgen Popp; Thomas Bocklitz. Comparability of Raman Spectroscopic Configurations: A Large Scale Cross-Laboratory Study. Analytical Chemistry 2020, 92, 15745 -15756.
AMA StyleShuxia Guo, Claudia Beleites, Ute Neugebauer, Sara Abalde-Cela, Nils Kristian Afseth, Fatima Alsamad, Suresh Anand, Cuauhtemoc Araujo-Andrade, Sonja Aškrabić, Ertug Avci, Monica Baia, Malgorzata Baranska, Enrico Baria, Luis A. E. Batista de Carvalho, Philippe de Bettignies, Alois Bonifacio, Franck Bonnier, Eva Maria Brauchle, Hugh J. Byrne, Igor Chourpa, Riccardo Cicchi, Frederic Cuisinier, Mustafa Culha, Marcel Dahms, Catalina David, Ludovic Duponchel, Shiyamala Duraipandian, Samir F. El-Mashtoly, David I. Ellis, Gauthier Eppe, Guillaume Falgayrac, Ozren Gamulin, Benjamin Gardner, Peter Gardner, Klaus Gerwert, Evangelos J. Giamarellos-Bourboulis, Sveinbjorn Gizurarson, Marcin Gnyba, Royston Goodacre, Patrick Grysan, Orlando Guntinas-Lichius, Helga Helgadottir, Vlasta Mohaček Grošev, Catherine Kendall, Roman Kiselev, Micha Kölbach, Christoph Krafft, Sivashankar Krishnamoorthy, Patrick Kubryck, Bernhard Lendl, Pablo Loza-Alvarez, Fiona M. Lyng, Susanne Machill, Cedric Malherbe, Monica Marro, Maria Paula M. Marques, Ewelina Matuszyk, Carlo Francesco Morasso, Myriam Moreau, Howbeer Muhamadali, Valentina Mussi, Ioan Notingher, Marta Z. Pacia, Francesco S. Pavone, Guillaume Penel, Dennis Petersen, Olivier Piot, Julietta V. Rau, Marc Richter, Maria Krystyna Rybarczyk, Hamideh Salehi, Katja Schenke-Layland, Sebastian Schlücker, Markus Schosserer, Karin Schütze, Valter Sergo, Faris Sinjab, Janusz Smulko, Ganesh D. Sockalingum, Clara Stiebing, Nick Stone, Valérie Untereiner, Renzo Vanna, Karin Wieland, Jürgen Popp, Thomas Bocklitz. Comparability of Raman Spectroscopic Configurations: A Large Scale Cross-Laboratory Study. Analytical Chemistry. 2020; 92 (24):15745-15756.
Chicago/Turabian StyleShuxia Guo; Claudia Beleites; Ute Neugebauer; Sara Abalde-Cela; Nils Kristian Afseth; Fatima Alsamad; Suresh Anand; Cuauhtemoc Araujo-Andrade; Sonja Aškrabić; Ertug Avci; Monica Baia; Malgorzata Baranska; Enrico Baria; Luis A. E. Batista de Carvalho; Philippe de Bettignies; Alois Bonifacio; Franck Bonnier; Eva Maria Brauchle; Hugh J. Byrne; Igor Chourpa; Riccardo Cicchi; Frederic Cuisinier; Mustafa Culha; Marcel Dahms; Catalina David; Ludovic Duponchel; Shiyamala Duraipandian; Samir F. El-Mashtoly; David I. Ellis; Gauthier Eppe; Guillaume Falgayrac; Ozren Gamulin; Benjamin Gardner; Peter Gardner; Klaus Gerwert; Evangelos J. Giamarellos-Bourboulis; Sveinbjorn Gizurarson; Marcin Gnyba; Royston Goodacre; Patrick Grysan; Orlando Guntinas-Lichius; Helga Helgadottir; Vlasta Mohaček Grošev; Catherine Kendall; Roman Kiselev; Micha Kölbach; Christoph Krafft; Sivashankar Krishnamoorthy; Patrick Kubryck; Bernhard Lendl; Pablo Loza-Alvarez; Fiona M. Lyng; Susanne Machill; Cedric Malherbe; Monica Marro; Maria Paula M. Marques; Ewelina Matuszyk; Carlo Francesco Morasso; Myriam Moreau; Howbeer Muhamadali; Valentina Mussi; Ioan Notingher; Marta Z. Pacia; Francesco S. Pavone; Guillaume Penel; Dennis Petersen; Olivier Piot; Julietta V. Rau; Marc Richter; Maria Krystyna Rybarczyk; Hamideh Salehi; Katja Schenke-Layland; Sebastian Schlücker; Markus Schosserer; Karin Schütze; Valter Sergo; Faris Sinjab; Janusz Smulko; Ganesh D. Sockalingum; Clara Stiebing; Nick Stone; Valérie Untereiner; Renzo Vanna; Karin Wieland; Jürgen Popp; Thomas Bocklitz. 2020. "Comparability of Raman Spectroscopic Configurations: A Large Scale Cross-Laboratory Study." Analytical Chemistry 92, no. 24: 15745-15756.
The estimation of steatosis in a liver graft is mandatory prior to liver transplantation, as the risk of graft failure increases with the level of infiltrated fat. However, the assessment of liver steatosis before transplantation is typically based on a qualitative or semiquantitative characterization by visual inspection and palpation and histological analysis. Thus, there is an unmet need for transplantation surgeons to have access to a diagnostic tool enabling an in situ fast classification of grafts prior to extraction. In this study, we have assessed an attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic method compatible with the requirements of an operation room for the evaluation of the lipid contents in human livers. A set of 20 human liver biopsies obtained from organs intended for transplantation were analyzed by expert pathologists, ATR-FTIR spectroscopy, lipid biochemical analysis, and UPLC-ESI(+/-)TOFMS for lipidomic profiling. Comparative analysis of multisource data showed strong correlations between ATR-FTIR, clinical, and lipidomic information. Results show that ATR-FTIR captures a global picture of the lipid composition of the liver, along with information for the quantification of the triradylglycerol content in liver biopsies. Although the methodology performance needs to be further validated, results support the applicability of ATR-FTIR for the in situ determination of the grade of liver steatosis at the operation room as a fast, quantitative method, as an alternative to the qualitative and subjective pathological examination.
David Pérez-Guaita; Marta Moreno-Torres; Ramiro Jover; Eugenia Pareja; Bernhard Lendl; Julia Kuligowski; Guillermo Quintás; Jose Vicente Castell. Toward Rapid Screening of Liver Grafts at the Operating Room Using Mid-infrared Spectroscopy. Analytical Chemistry 2020, 92, 14542 -14549.
AMA StyleDavid Pérez-Guaita, Marta Moreno-Torres, Ramiro Jover, Eugenia Pareja, Bernhard Lendl, Julia Kuligowski, Guillermo Quintás, Jose Vicente Castell. Toward Rapid Screening of Liver Grafts at the Operating Room Using Mid-infrared Spectroscopy. Analytical Chemistry. 2020; 92 (21):14542-14549.
Chicago/Turabian StyleDavid Pérez-Guaita; Marta Moreno-Torres; Ramiro Jover; Eugenia Pareja; Bernhard Lendl; Julia Kuligowski; Guillermo Quintás; Jose Vicente Castell. 2020. "Toward Rapid Screening of Liver Grafts at the Operating Room Using Mid-infrared Spectroscopy." Analytical Chemistry 92, no. 21: 14542-14549.
We report a mid-IR transmission setup for the analysis of the protein amide I and amide II band in aqueous solutions that achieves a limit of detection as low as 0.0025 mg mL-1 (outperforming our previous results and other state-of-the-art mid-IR based techniques by almost an order of magnitude). This large improvement is made possible by combining a latest generation external cavity-quantum cascade laser (EC-QCL) operated at room temperature with an optimized double-beam optical setup that adjusts the path length (26 µm) to ensure robust sample handling. For minimizing the noise introduced by the high intensity laser light source, a thermoelectrically cooled mercury cadmium telluride balanced detection module was employed. In this way, noise levels better by a factor of up to 20 were achieved compared to single channel measurements. Characteristic spectral features of proteins with different secondary structures were successfully identified at concentrations as low as 0.1 mg mL-1. Furthermore, highly linear response was demonstrated for concentrations between 0.05 mg mL-1 and 10 mg mL-1. The total acquisition time of the setup can be adapted to fulfill the required sensitivity of the protein measurements and to ensure maximum flexibility for future applications. The presented setup combines high sensitivity, large optical path lengths as well as short measurement times and thus outperforms previous research type EC-QCL setups as well as commercially available instruments. This opens a wide range of future applications including protein-ligand interaction studies as well as qualitative and quantitative analysis of proteins in complex matrices such as found in up- and downstream bioprocess monitoring and similar challenging applications which can not readily be met conventional mid-FT-IR spectroscopy.
Christopher Karim Akhgar; Georg Ramer; Mateusz Żbik; Artur Trajnerowicz; Jarosław Pawluczyk; Andreas Schwaighofer; Bernhard Lendl. The Next Generation of IR Spectroscopy: EC-QCL-Based Mid-IR Transmission Spectroscopy of Proteins with Balanced Detection. Analytical Chemistry 2020, 92, 9901 -9907.
AMA StyleChristopher Karim Akhgar, Georg Ramer, Mateusz Żbik, Artur Trajnerowicz, Jarosław Pawluczyk, Andreas Schwaighofer, Bernhard Lendl. The Next Generation of IR Spectroscopy: EC-QCL-Based Mid-IR Transmission Spectroscopy of Proteins with Balanced Detection. Analytical Chemistry. 2020; 92 (14):9901-9907.
Chicago/Turabian StyleChristopher Karim Akhgar; Georg Ramer; Mateusz Żbik; Artur Trajnerowicz; Jarosław Pawluczyk; Andreas Schwaighofer; Bernhard Lendl. 2020. "The Next Generation of IR Spectroscopy: EC-QCL-Based Mid-IR Transmission Spectroscopy of Proteins with Balanced Detection." Analytical Chemistry 92, no. 14: 9901-9907.
The bacterium E. coli is one of the most important hosts for recombinant protein production. The benefits are high growth rates, inexpensive media, and high protein titers. However, complex proteins with high molecular weight and many disulfide bonds are expressed as inclusion bodies (IBs). In the last decade, the overall perception of these IBs being not functional proteins changed, as enzyme activity was found within IBs. Several applications for direct use of IBs are already reported in literature. While fluorescent proteins or protein tags are used for determination of IB activity to date, direct measurements of IB protein activity are scacre. The expression of recombinant hyaluronidase from Apis mellifera in E. coli BL21(DE3) was analyzed using a face centered design of experiment approach. Hyaluronidase is a hard to express protein and imposes a high metabolic burden to the host. Conditions giving a high specific IB titer were found at 25 °C at low specific substrate uptake rates and induction times of 2 to 4 h. The protein activity of hyaluronidase IBs was verified using (Fourier transform) FT-IR spectroscopy. Degradation of the substrate hyaluronan occurred at increased rates with higher IB concentrations. Active recombinant hyaluronidase IBs can be immediately used for direct degradation of hyaluronan without further down streaming steps. FT-IR spectroscopy was introduced as a method for tracking IB activity and showed differences in degradation behavior of hyaluronan dependent on the applied active IB concentration.
Andreas Schwaighofer; Sarah Ablasser; Laurin Lux; Julian Kopp; Christoph Herwig; Oliver Spadiut; Bernhard Lendl; Christoph Slouka. Production of Active Recombinant Hyaluronidase Inclusion Bodies from Apis mellifera in E. coli Bl21(DE3) and characterization by FT-IR Spectroscopy. International Journal of Molecular Sciences 2020, 21, 3881 .
AMA StyleAndreas Schwaighofer, Sarah Ablasser, Laurin Lux, Julian Kopp, Christoph Herwig, Oliver Spadiut, Bernhard Lendl, Christoph Slouka. Production of Active Recombinant Hyaluronidase Inclusion Bodies from Apis mellifera in E. coli Bl21(DE3) and characterization by FT-IR Spectroscopy. International Journal of Molecular Sciences. 2020; 21 (11):3881.
Chicago/Turabian StyleAndreas Schwaighofer; Sarah Ablasser; Laurin Lux; Julian Kopp; Christoph Herwig; Oliver Spadiut; Bernhard Lendl; Christoph Slouka. 2020. "Production of Active Recombinant Hyaluronidase Inclusion Bodies from Apis mellifera in E. coli Bl21(DE3) and characterization by FT-IR Spectroscopy." International Journal of Molecular Sciences 21, no. 11: 3881.
A quantum cascade laser-based sensor for ambient air monitoring is presented and five gases, affecting the air quality, can be quantified. The light sources are selected to measure CO, NO, NO2, N2O and SO2. The footprint of the measurement setup is designed to fit in two standard 19” rack (48 cm × 65 cm) with 4 height units (18 cm) whereas one is holding the optical components and the other one contains the electronics and data processing unit. The concentrations of the individual analytes are measured using 2f-Wavelength Modulation Spectroscopy (2f-WMS) and a commercially available multipass gas cell defines the optical path. In addition, CO can also be measured with a dispersion-based technique, which allows one to cover a wider concentration range than 2f-WMS. The performance of this prototype has been evaluated in the lab and detection limits in the range of 1ppbv have been achieved. Finally, the applicability of this prototype for ambient air monitoring is shown in a five-week measurement campaign in cooperation with the Municipal Department for Environmental Protection (MA 22) of Vienna, Austria.
Andreas Genner; Pedro Martín-Mateos; Harald Moser; Bernhard Lendl. A Quantum Cascade Laser-Based Multi-Gas Sensor for Ambient Air Monitoring. Sensors 2020, 20, 1850 .
AMA StyleAndreas Genner, Pedro Martín-Mateos, Harald Moser, Bernhard Lendl. A Quantum Cascade Laser-Based Multi-Gas Sensor for Ambient Air Monitoring. Sensors. 2020; 20 (7):1850.
Chicago/Turabian StyleAndreas Genner; Pedro Martín-Mateos; Harald Moser; Bernhard Lendl. 2020. "A Quantum Cascade Laser-Based Multi-Gas Sensor for Ambient Air Monitoring." Sensors 20, no. 7: 1850.
In this work, we present a fully 3D-printed module for attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy ready for use in commercial FTIR spectrometers. The developed setup stands out in terms of robustness and ease of sample application. Rapid prototyping paired with theoretical considerations were employed to design and fabricate the module. Cost-efficient commercial available silicon and germanium ATR crystals prepared from double-sided polished wafers were mounted in the setup. While low-noise levels and stability bear comparison with commercial systems, the multibounce ATR crystal's long interaction pathlengths as well as their interchangeability turns the presented ATR module into an even more sophisticated tool. The versatility of the proposed setup is demonstrated for various spectroscopic challenges: Curing of a cyanoacrylate and a two-component epoxy based adhesive was monitored by tracking polymerization processes at room and high temperatures. To emphasize potential applications of the disposable ATR module in life science studies exploring potential biohazardous samples, mid-IR spectra of Escherichia coli and bovine serum albumin were recorded. The total printing time of the ATR module is 10.5 h, enabling overnight fabrication at a total cost ranging from 150 to 613 €, making the high versatility of ATR spectroscopy accessible to a broader audience. This proves the potential of 3D printing to generate optical instruments tailored to the needs of individual analytical problems.
Bettina Baumgartner; Stephan Freitag; Bernhard Lendl. 3D Printing for Low-Cost and Versatile Attenuated Total Reflection Infrared Spectroscopy. Analytical Chemistry 2020, 92, 4736 -4741.
AMA StyleBettina Baumgartner, Stephan Freitag, Bernhard Lendl. 3D Printing for Low-Cost and Versatile Attenuated Total Reflection Infrared Spectroscopy. Analytical Chemistry. 2020; 92 (7):4736-4741.
Chicago/Turabian StyleBettina Baumgartner; Stephan Freitag; Bernhard Lendl. 2020. "3D Printing for Low-Cost and Versatile Attenuated Total Reflection Infrared Spectroscopy." Analytical Chemistry 92, no. 7: 4736-4741.
Fourier transform infrared (FT-IR) spectrometers have been the dominant technology in the field of mid-infrared (mid-IR) spectroscopy for decades. Supercontinuum laser sources operating in the mid-IR spectral region now offer the potential to enrich the field of FT-IR spectroscopy due to their distinctive properties, such as high-brightness, broadband spectral coverage and enhanced stability. In our contribution, we introduce this advanced light source as a replacement for conventional thermal emitters. Furthermore, an approach to efficient coupling of pulsed mid-IR supercontinuum sources to FT-IR spectrometers is proposed and considered in detail. The experimental part is devoted to pulse-to-pulse energy fluctuations of the applied supercontinuum laser, performance of the system, as well as the noise and long-term stability. Comparative measurements performed with a conventional FT-IR instrument equipped with a thermal emitter illustrate that similar noise levels can be achieved with the supercontinuum-based system. The analytical performance of the supercontinuum-based FT-IR spectrometer was tested for a concentration series of aqueous formaldehyde solutions in a liquid flow cell (500 µm path length) and compared with the conventional FT-IR (130 µm path length). The results show a four-times-enhanced detection limit due to the extended path length enabled by the high brightness of the laser. In conclusion, FT-IR spectrometers equipped with novel broadband mid-IR supercontinuum lasers could outperform traditional systems providing superior performance, e.g., interaction path lengths formerly unattainable, while maintaining low noise levels known from highly stable thermal emitters.
Ivan Zorin; Jakob Kilgus; Kristina Duswald; Bernhard Lendl; Bettina Heise; Markus Brandstetter. Sensitivity-Enhanced Fourier Transform Mid-Infrared Spectroscopy Using a Supercontinuum Laser Source. Applied Spectroscopy 2020, 74, 485 -493.
AMA StyleIvan Zorin, Jakob Kilgus, Kristina Duswald, Bernhard Lendl, Bettina Heise, Markus Brandstetter. Sensitivity-Enhanced Fourier Transform Mid-Infrared Spectroscopy Using a Supercontinuum Laser Source. Applied Spectroscopy. 2020; 74 (4):485-493.
Chicago/Turabian StyleIvan Zorin; Jakob Kilgus; Kristina Duswald; Bernhard Lendl; Bettina Heise; Markus Brandstetter. 2020. "Sensitivity-Enhanced Fourier Transform Mid-Infrared Spectroscopy Using a Supercontinuum Laser Source." Applied Spectroscopy 74, no. 4: 485-493.
We developed a top-irradiated, liquid-phase attenuated total reflectance Fourier transform infrared (ATR-FTIR) setup that allows time-resolved investigations of both Pt particle growth during in situ photodeposition via monitoring of the Pt0–COads band on TiO2 thin films as well as the photooxidation of methanol in aqueous environments. Obtained ATR-FTIR data sets were analyzed via multivariate curve resolution-alternating least squares (MCR-ALS), which enabled us to clearly differentiate various reaction pathways for different Pt loadings at otherwise fixed reaction conditions (i.e., methanol concentration, UV intensity). At the highest Pt loading (nominal concentration of 2.7 wt %), photooxidation of methanol occurs via direct oxidation through a formaldehyde intermediate to CO2, whereas the lower Pt loadings of 0.7 and 1.4 wt % favor a side reaction that includes methyl formate as an intermediate. These findings were correlated with the formation of different CO binding sites on Pt during photodeposition, and we presume that changes in the reaction pathway depend on the number rather than the nature of active available Pt sites. Complementary ex situ characterizations of the thin films by transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP-MS) were performed, delivering information on the generated Pt nanoparticles and structural changes of TiO2. The presented optical setup paves the way for fundamental studies of heterogeneous catalytic reactions as close as possible to their actual use in aqueous systems.
Greta M. Haselmann; Bettina Baumgartner; Jia Wang; Karin Wieland; Tushar Gupta; Christopher Herzig; Andreas Limbeck; Bernhard Lendl; Dominik Eder. In Situ Pt Photodeposition and Methanol Photooxidation on Pt/TiO2: Pt-Loading-Dependent Photocatalytic Reaction Pathways Studied by Liquid-Phase Infrared Spectroscopy. ACS Catalysis 2020, 10, 2964 -2977.
AMA StyleGreta M. Haselmann, Bettina Baumgartner, Jia Wang, Karin Wieland, Tushar Gupta, Christopher Herzig, Andreas Limbeck, Bernhard Lendl, Dominik Eder. In Situ Pt Photodeposition and Methanol Photooxidation on Pt/TiO2: Pt-Loading-Dependent Photocatalytic Reaction Pathways Studied by Liquid-Phase Infrared Spectroscopy. ACS Catalysis. 2020; 10 (5):2964-2977.
Chicago/Turabian StyleGreta M. Haselmann; Bettina Baumgartner; Jia Wang; Karin Wieland; Tushar Gupta; Christopher Herzig; Andreas Limbeck; Bernhard Lendl; Dominik Eder. 2020. "In Situ Pt Photodeposition and Methanol Photooxidation on Pt/TiO2: Pt-Loading-Dependent Photocatalytic Reaction Pathways Studied by Liquid-Phase Infrared Spectroscopy." ACS Catalysis 10, no. 5: 2964-2977.
Strong anion-exchange materials carry a positive charge that allows them to trap and concentrate anions while releasing other anions. Here, we introduced a quaternary ammonium anion exchange group into mesoporous silica films coated on attenuated total reflection (ATR) crystals to enrich nitrate from aqueous phase in the volume probed by the evanescent field. The ion-exchange and enrichment capabilities of the films were characterized using FTIR spectroscopy. Thereby fast analyte enrichment and full sensor recovery were observed. In addition, high enrichment factors of up to 1600 were achieved. After characterization, these coated ATR crystals were used in a dedicated ATR-IR filtometer comprising a Fabry-Pérot filter detector unit and a miniaturized thermal emitter with a overall dimensions of only 80 mm × 120 mm × 70 mm. The filter covered the spectral region between 1250–1800 cm−1 allowing for recording IR spectra of nitrate enriched into the mesoporous silica film. The sensor was calibrated using the Langmuir adsorption model as calibration function. From this a limit of detection of 1.2 mg L−1 was derived for the ATR-IR filtometer. This emphasizes the high potential of functionalized mesoporous silica films combined with low-cost filtometers for portable water sensors.
Bettina Baumgartner; Stephan Freitag; Christoph Gasser; Bernhard Lendl. A pocket-sized 3D-printed attenuated total reflection-infrared filtometer combined with functionalized silica films for nitrate sensing in water. Sensors and Actuators B: Chemical 2020, 310, 127847 .
AMA StyleBettina Baumgartner, Stephan Freitag, Christoph Gasser, Bernhard Lendl. A pocket-sized 3D-printed attenuated total reflection-infrared filtometer combined with functionalized silica films for nitrate sensing in water. Sensors and Actuators B: Chemical. 2020; 310 ():127847.
Chicago/Turabian StyleBettina Baumgartner; Stephan Freitag; Christoph Gasser; Bernhard Lendl. 2020. "A pocket-sized 3D-printed attenuated total reflection-infrared filtometer combined with functionalized silica films for nitrate sensing in water." Sensors and Actuators B: Chemical 310, no. : 127847.
Acquisition of classical absorption spectra of liquids in the mid-IR range with quantum cascade lasers (QCLs) is often limited in sensitivity by noise from the laser source. Alternatively, measurement of molecular dispersion (i.e., refractive index) spectra poses an experimental approach that is immune to intensity fluctuations and further offers a direct relationship between the recorded signal and the sample concentration. In this work, we present an external cavity quantum cascade laser (EC-QCL) based Mach–Zehnder interferometer setup to determine dispersion spectra of liquid samples. We present two approaches for acquisition of refractive index spectra and compare the qualitative experimental results. Furthermore, the performance for quantitative analysis is evaluated. Finally, multivariate analysis of a spectrally complex mixture comprising three different sugars is performed. The obtained figures of merit by partial least squares (PLS) regression modelling compare well with standard absorption spectroscopy, demonstrating the potential of the introduced dispersion spectroscopic method for quantitative chemical analysis.
Stefan Lindner; Jakob Hayden; Andreas Schwaighofer; Tobias Wolflehner; Christian Kristament; María González-Cabrera; Stefan Zlabinger; Bernhard Lendl. External Cavity Quantum Cascade Laser-Based Mid-Infrared Dispersion Spectroscopy for Qualitative and Quantitative Analysis of Liquid-Phase Samples. Applied Spectroscopy 2020, 74, 452 -459.
AMA StyleStefan Lindner, Jakob Hayden, Andreas Schwaighofer, Tobias Wolflehner, Christian Kristament, María González-Cabrera, Stefan Zlabinger, Bernhard Lendl. External Cavity Quantum Cascade Laser-Based Mid-Infrared Dispersion Spectroscopy for Qualitative and Quantitative Analysis of Liquid-Phase Samples. Applied Spectroscopy. 2020; 74 (4):452-459.
Chicago/Turabian StyleStefan Lindner; Jakob Hayden; Andreas Schwaighofer; Tobias Wolflehner; Christian Kristament; María González-Cabrera; Stefan Zlabinger; Bernhard Lendl. 2020. "External Cavity Quantum Cascade Laser-Based Mid-Infrared Dispersion Spectroscopy for Qualitative and Quantitative Analysis of Liquid-Phase Samples." Applied Spectroscopy 74, no. 4: 452-459.
Water affects the amplitude of photoacoustic signals from many gas phase molecules. In quartz-enhanced photoacoustic (QEPAS) measurements of CO excited at the fundamental vibrational resonance of CO, the photoacoustic signal decreases with increasing humidity, reaches a pronounced minimum at ~0.19%V, and increases with humidity for higher water contents. This peculiar trend is explained by competing endothermal and exothermal pathways of the vibrational relaxation of CO in N2 and H2O. Near-resonant vibrational–vibrational transfer from CO to N2, whose vibrational frequency is 188 cm−1 higher than in CO, consumes thermal energy, yielding a kinetic cooling effect. In contrast, vibrational relaxation via H2O is fast and exothermal, and hence counteracts kinetic cooling, explaining the observed trend. A detailed kinetic model for collisional relaxation of CO in N2 and H2O is presented. Simulations using rate constants obtained from literature were performed and compared to humidity dependent QEPAS experiments at varying pressure. Agreement between the experiments and simulations confirmed the validity of the model. The kinetic model can be used to identify optimized experimental conditions for sensing CO and can be readily adapted to include further collision partners.
Jakob Hayden; Bettina Baumgartner; Bernhard Lendl. Anomalous Humidity Dependence in Photoacoustic Spectroscopy of CO Explained by Kinetic Cooling. Applied Sciences 2020, 10, 843 .
AMA StyleJakob Hayden, Bettina Baumgartner, Bernhard Lendl. Anomalous Humidity Dependence in Photoacoustic Spectroscopy of CO Explained by Kinetic Cooling. Applied Sciences. 2020; 10 (3):843.
Chicago/Turabian StyleJakob Hayden; Bettina Baumgartner; Bernhard Lendl. 2020. "Anomalous Humidity Dependence in Photoacoustic Spectroscopy of CO Explained by Kinetic Cooling." Applied Sciences 10, no. 3: 843.
A novel external cavity-quantum cascade laser (EC-QCL)-based setup for mid-IR transmission spectroscopy in the amide I and amide II region was employed for monitoring pH-induced changes of protein secondary structure. pH titration of β-lactoglobulin revealed unfolding of the native β-sheet secondary structure occurring at basic pH. Chemometric analysis of the dynamic IR spectra was performed by multivariate curve resolution-alternating least squares (MCR-ALS). Using this approach, spectral and abundance distribution profiles of the conformational transition were obtained. A proper post-processing procedure was implemented allowing to extract information about pure protein spectra and spurious signals that may interfere in the interpretation of the system. This work demonstrates the potential and versatility of the EC-QCL-based IR transmission setup for flow-through applications, benefitting from the high available optical path length.
Andreas Schwaighofer; Mirta R. Alcaraz; Laurin Lux; Bernhard Lendl. pH titration of β-lactoglobulin monitored by laser-based Mid-IR transmission spectroscopy coupled to chemometric analysis. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2019, 226, 117636 .
AMA StyleAndreas Schwaighofer, Mirta R. Alcaraz, Laurin Lux, Bernhard Lendl. pH titration of β-lactoglobulin monitored by laser-based Mid-IR transmission spectroscopy coupled to chemometric analysis. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 2019; 226 ():117636.
Chicago/Turabian StyleAndreas Schwaighofer; Mirta R. Alcaraz; Laurin Lux; Bernhard Lendl. 2019. "pH titration of β-lactoglobulin monitored by laser-based Mid-IR transmission spectroscopy coupled to chemometric analysis." Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 226, no. : 117636.
Sensitivity of evanescent wave sensing of gaseous species can be vastly increased by enrichment materials that locally concentrate the analyte on the sensor. Here, we investigate functionalized mesoporous silica films as versatile enrichment layer for sensing volatile organic compounds (VOCs) from gas-phase. Attenuated total reflection (ATR) crystals were coated with silica films of different pore sizes and their capability to enrich three different aromatic hydrocarbons from a vapor stream was studied by means of Fourier Transform infrared (FTIR) spectroscopy. Thereby, single-digit ppmv limits of detection (LOD) were achieved with an effective path length of only 6.3 μm. The selectivity introduced by the functionalization of the silica films effectively minimized interferences of water vapor, which gave access to the spectral fingerprint region between 1550 and 1450 cm−1. This allowed to discriminate and quantify toluene, p-xylene and 1,2,4-trimethylbenzene in multicomponent mixtures at high humidity. Fast response and regeneration times and enrichment factors up to 32 000 showcase the high potential of this material for evanescent wave sensing.
Bettina Baumgartner; Jakob Hayden; Bernhard Lendl. Mesoporous silica films for sensing volatile organic compounds using attenuated total reflection spectroscopy. Sensors and Actuators B: Chemical 2019, 302, 127194 .
AMA StyleBettina Baumgartner, Jakob Hayden, Bernhard Lendl. Mesoporous silica films for sensing volatile organic compounds using attenuated total reflection spectroscopy. Sensors and Actuators B: Chemical. 2019; 302 ():127194.
Chicago/Turabian StyleBettina Baumgartner; Jakob Hayden; Bernhard Lendl. 2019. "Mesoporous silica films for sensing volatile organic compounds using attenuated total reflection spectroscopy." Sensors and Actuators B: Chemical 302, no. : 127194.