Experimental surface pressure ($\mathsf{\pi }$) and electric surface potential ($\Delta \mathrm{V}$) isotherms were measured for membrane lipids, including the following phosphatidylcholines (PCs)—1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC); 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC); 1,2-diarachidoyl-sn-glycero-3-phosphocholine (DAPC); and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). In addition, other phospholipids, such as phosphatidylethanolamines (represented by 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE)) and sphingolipids (represented by N-(hexadecanoyl)-sphing-4-enine-1-phosphocholine (SM)) were also studied. The experimental apparent dipole moments (${\mathsf{\mu }}_{\mathrm{A}}^{\exp }$) of the abovementioned lipids were determined using the Helmholtz equation. The particular contributions to the apparent dipole moments of the investigated molecules connected with their polar (${\mathsf{\mu }}_{\perp }^{\mathrm{p}}$) and apolar parts (${\mathsf{\mu }}_{\perp }^{\mathrm{a}}$) were theoretically calculated for geometrically optimized systems. Using a three-layer capacitor model, introducing the group’s apparent dipole moments (calculated herein) and adopting values from other papers to account for the reorientation of water molecules (${\mathsf{\mu }}_{\perp }^{\mathrm{w}}/{\mathsf{\epsilon }}_{\mathrm{w}}$), as well as the for the local dielectric permittivity in the vicinity of the polar (${\mathsf{\epsilon }}_{\mathrm{p}}$) and apolar (${\mathsf{\epsilon }}_{\mathrm{a}}$) groups, the apparent dipole moments of the investigated molecules were calculated (${\mathsf{\mu }}_{\mathrm{A}}^{\mathrm{calc}}$). Since the comparison of the two values (experimental and calculated) resulted in large discrepancies, we developed a new methodology that correlates the results from density functional theory (DFT) molecular modeling with experimentally determined values using multiple linear regression. From the fitted model, the following contributions to the apparent dipole moments were determined: ${\mathsf{\mu }}_{\perp }^{\mathrm{w}}/{\mathsf{\epsilon }}_{\mathrm{w}}=-1.8\pm 1.4 D$; ${\mathsf{\epsilon }}_{\mathrm{p}}=10.2\pm 7.0$ and ${\mathsf{\epsilon }}_{\mathrm{a}}=0.95\pm 0.52$). Local dielectric permittivity in the vicinity of apolar groups (${\mathsf{\epsilon }}_{\mathrm{a}}$) is much lower compared to that in the vicinity of polar moieties (${\mathsf{\epsilon }}_{\mathrm{p}}$), which is in line with the tendency observed by other authors studying simple molecules with small polar groups. A much higher value for the contributions from the reorientation of water molecules (${\mathsf{\mu }}_{\perp }^{\mathrm{w}}/{\mathsf{\epsilon }}_{\mathrm{w}}$) has been interpreted as resulting from bulky and strongly hydrated polar groups of phospholipids.

The integrity of the chromatin structure is essential to every process occurring within eukaryotic nuclei. However, there are no reliable tools to decipher the molecular composition of metaphase chromosomes. Here, we have applied infrared nanospectroscopy (AFM-IR) to demonstrate molecular difference between eu- and heterochromatin and generate infrared maps of single metaphase chromosomes revealing detailed information on their molecular composition, with nanometric lateral spatial resolution. AFM-IR coupled with principal component analysis has confirmed that chromosome areas containing euchromatin and heterochromatin are distinguishable based on differences in the degree of methylation. AFM-IR distribution of eu- and heterochromatin was compared to standard fluorescent staining. We demonstrate the ability of our methodology to locate spatially the presence of anticancer drug sites in metaphase chromosomes and cellular nuclei. We show that the anticancer 'rule breaker' platinum compound [Pt[N(p-HC₆F₄)CH₂]₂py₂] preferentially binds to heterochromatin, forming localized discrete foci due to condensation of DNA interacting with the drug. Given the importance of DNA methylation in the development of nearly all types of cancer, there is potential for infrared nanospectroscopy to be used to detect gene expression/suppression sites in the whole genome and to become an early screening tool for malignancy.

Cholesterol oxidation products (called oxysterols) are involved in many biological processes, showing both negative (e.g., neurodegenerative) and positive (e.g., antiviral and antimicrobial) effects. The physiological activity of oxysterols is undoubtedly closely related to their structure (i.e., the type and location of the additional polar group in the cholesterol skeleton). In this paper, we focus on determining how a seemingly minor structural change (introduction of a hydroxyl moiety at C(24), C(25), or C(27) in the isooctyl chain of cholesterol) affects the organization of the resulting molecules at the phase boundary. In our research, we supplemented the classic Langmuir monolayer technique, based on the surface pressure and electric surface potential isotherms, with microscopic (BAM) and spectroscopic (PM-IRRAS) techniques, as well as theoretical calculations (DFT and MD). This allowed us to show that 24-OH behaves more like cholesterol and forms stable, rigid monolayers. On the other hand, 27-OH, similar to 25-OH, undergoes the phase transition from monolayer to bilayer structures. Theoretical calculations enabled us to conclude that the formation of bilayers from 27-OH or 25-OH is possible due to the hydrogen bonding between adjacent oxysterol molecules. This observation may help to understand the factors responsible for the unique biological activity (including antiviral and antimicrobial) of 27-OH and 25-OH compared to other oxysterols.

Complexes like the studied DNA and didecyldimethylammonium chloride are promising materials for organic electronics and photonics. Water content in this material as the solid state is a key factor for its electronics properties and microstructure. DNA complex was subjected to controlled hydration from gaseous phase and next studied by ¹H-nuclear magnetic resonance spectroscopy. Variations of spin-spin and spin-lattice relaxation times as a function of hydration level are reported. Formation of tightly and loosely bound water fractions at rehydration process is discussed.

Parkinson’s disease (PD) is a progressive, neurodegenerative disorder primarily affecting dopaminergic neuronal systems, with impaired motor function as a consequence. The most effective treatment for PD remains the administration of oral levodopa (LD). Long-term LD treatment is frequently associated with motor fluctuations and dyskinesias, which exert a serious impact on a patient’s quality of life. The aim of our study was to determine the pharmacokinetics of LD: used as monotherapy or in combination with ropinirole, in patients with advanced PD. Furthermore, an effect of ropinirole on the pharmacokinetics of 3-OMD (a major LD metabolite) was assessed. We also investigated the correlation between the pharmacokinetic parameters of LD and 3-OMD and the occurrence of motor complications. Twenty-seven patients with idiopathic PD participated in the study. Thirteen patients received both LD and ropinirole, and fourteen administered LD monotherapy. Among 27 patients, twelve experienced fluctuations and/or dyskinesias, whereas fifteen were free of motor complications. Inter- and intra-individual variation in the LD and 3-OMD concentrations were observed. There were no significant differences in the LD and 3-OMD concentrations between the patients treated with a combined therapy of LD and ropinirole, and LD monotherapy. There were no significant differences in the LD concentrations in patients with and without motor complications; however, plasma 3-OMD levels were significantly higher in patients with motor complications. A linear one-compartment pharmacokinetic model with the first-order absorption was adopted for LD and 3-OMD. Only mean exit (residence) time for 3-OMD was significantly shorter in patients treated with ropinirole. Lag time, V/F, CL/F and t_max of LD had significantly lower values in patients with motor complications. On the other hand, AUC were significantly higher in these patients, both for LD and 3-OMD. 3-OMD C_max was significantly higher in patients with motor complications as well. Our results showed that ropinirole does not influence LD or 3-OMD concentrations. Higher 3-OMD levels play a role in inducing motor complications during long-term levodopa therapy.