Sleep restriction and circadian clock disruption are associated with metabolic disorders such as obesity, insulin resistance, and diabetes. The metabolic pathways involved in human sleep, however, have yet to be investigated with the use of a metabolomics approach. Here we have used untargeted and targeted liquid chromatography (LC)/MS metabolomics to examine the effect of acute sleep deprivation on plasma metabolite rhythms. Twelve healthy young male subjects remained in controlled laboratory conditions with respect to environmental light, sleep, meals, and posture during a 24-h wake/sleep cycle, followed by 24 h of wakefulness. Two-hourly plasma samples collected over the 48 h period were analyzed by LC/MS. Principal component analysis revealed a clear time of day variation with a significant cosine fit during the wake/sleep cycle and during 24 h of wakefulness in untargeted and targeted analysis. Of 171 metabolites quantified, daily rhythms were observed in the majority (n = 109), with 78 of these maintaining their rhythmicity during 24 h of wakefulness, most with reduced amplitude (n = 66). During sleep deprivation, 27 metabolites (tryptophan, serotonin, taurine, 8 acylcarnitines, 13 glycerophospholipids, and 3 sphingolipids) exhibited significantly increased levels compared with during sleep. The increased levels of serotonin, tryptophan, and taurine may explain the antidepressive effect of acute sleep deprivation and deserve further study. This report, to our knowledge the first of metabolic profiling during sleep and sleep deprivation and characterization of 24 h rhythms under these conditions, offers a novel view of human sleep/wake regulation. Significance Sleep restriction and circadian clock disruption are associated with metabolic disorders including obesity and diabetes; this association can be studied by using the powerful tool of metabolomics. By using liquid chromatography/MS metabolomics, we have characterized plasma metabolites that were significantly affected by acute sleep deprivation (mainly lipids and acylcarnitines), all increasing during sleep deprivation. Observed increased levels of serotonin, tryptophan, and taurine may explain the antidepressive effect of sleep deprivation and deserve further study. Clear daily rhythms were observed in most metabolites, with 24 h wakefulness mainly reducing the amplitude of these rhythms. Our results further the understanding of sleep/wake regulation and the associated metabolic processes, and will be vital when using metabolic profiling to identify robust biomarkers for disease states and drug efficacy.

Distance distribution information obtained by pulsed dipolar EPR spectroscopy provides an important contribution to many studies in structural biology. Increasingly, such information is used in integrative structural modeling, where it delivers unique restraints on the width of conformational ensembles. In order to ensure reliability of the structural models and of biological conclusions, we herein define quality standards for sample preparation and characterization, for measurements of distributed dipole–dipole couplings between paramagnetic labels, for conversion of the primary time-domain data into distance distributions, for interpreting these distributions, and for reporting results. These guidelines are substantiated by a multi-laboratory benchmark study and by analysis of data sets with known distance distribution ground truth. The study and the guidelines focus on proteins labeled with nitroxides and on double electron–electron resonance (DEER aka PELDOR) measurements and provide suggestions on how to proceed analogously in other cases.

S and full research articles published in SLEEP, the official journal of the APSS. Sleep and sleep disorder scientific findings.

This study investigated the impact of sleep deprivation on the human circadian system. Plasma melatonin and cortisol levels and leukocyte expression levels of 12 genes were examined over 48 h (sleep vs. no-sleep nights) in 12 young males (mean ± SD: 23 ± 5 yrs). During one night of total sleep deprivation, BMAL1 expression was suppressed, the heat shock gene HSPA1B expression was induced, and the amplitude of the melatonin rhythm increased, whereas other high-amplitude clock gene rhythms (e.g., PER1-3, REV-ERBα) remained unaffected. These data suggest that the core clock mechanism in peripheral oscillators is compromised during acute sleep deprivation.

Electron paramagnetic resonance (EPR) distance measurements are making increasingly important contributions to the studies of biomolecules by providing highly accurate geometric constraints. Combining double‐histidine motifs with Cu^II spin labels can further increase the precision of distance measurements. It is also useful for proteins containing essential cysteines that can interfere with thiol‐specific labelling. However, the non‐covalent Cu^II coordination approach is vulnerable to low binding‐affinity. Herein, dissociation constants (K_D) are investigated directly from the modulation depths of relaxation‐induced dipolar modulation enhancement (RIDME) EPR experiments. This reveals low‐ to sub‐μm Cu^II K_Ds under EPR distance measurement conditions at cryogenic temperatures. We show the feasibility of exploiting the double‐histidine motif for EPR applications even at sub‐μm protein concentrations in orthogonally labelled Cu^II–nitroxide systems using a commercial Q‐band EPR instrument.