Deuterated amino acids have been recognized for their utility in drug development, for facilitating nuclear magnetic resonance (NMR) analysis, and as probes for enzyme mechanism. Small molecule-based ...methods for the site-selective synthesis of deuterated amino acids typically involve de novo synthesis of the compound from deuterated precursors. In comparison, enzymatic methods for introducing deuterium offer improved efficiency, operating directly on free amino acids to achieve hydrogen-deuterium (H/D) exchange. However, site selectivity remains a significant challenge for enzyme-mediated deuteration, limiting access to desirable deuteration motifs. Here, we use enzyme-catalyzed deuteration, combined with steady-state kinetic analysis and ultraviolet (UV)–vis spectroscopy to probe the mechanism of a two-protein system responsible for the biosynthesis of l-allo-Ile. We show that an aminotransferase (DsaD) can pair with a small partner protein (DsaE) to catalyze Cα and Cβ H/D exchange of amino acids, while reactions without DsaE lead exclusively to Cα-deuteration. With conditions for improved catalysis, we evaluate the substrate scope for Cα/Cβ-deuteration and demonstrate the utility of this system for preparative-scale, selective labeling of amino acids.
The dimeric diketopiperazine (DKPs) alkaloids are a diverse family of natural products (NPs) whose unique structural architectures and biological activities have inspired the development of new ...synthetic methodologies to access these molecules. However, catalyst-controlled methods that enable the selective formation of constitutional and stereoisomeric dimers from a single monomer are lacking. To resolve this long-standing synthetic challenge, we sought to characterize the biosynthetic enzymes that assemble these NPs for application in biocatalytic syntheses. Genome mining enabled identification of the cytochrome P450, NzeB (Streptomyces sp. NRRL F-5053), which catalyzes both intermolecular carbon–carbon (C–C) and carbon–nitrogen (C–N) bond formation. To identify the molecular basis for the flexible site-selectivity, stereoselectivity, and chemoselectivity of NzeB, we obtained high-resolution crystal structures (1.5 Å) of the protein in complex with native and non-native substrates. This, to our knowledge, represents the first crystal structure of an oxidase catalyzing direct, intermolecular C–H amination. Site-directed mutagenesis was utilized to assess the role individual active-site residues play in guiding selective DKP dimerization. Finally, computational approaches were employed to evaluate plausible mechanisms regarding NzeB function and its ability to catalyze both C–C and C–N bond formation. These results provide a structural and computational rationale for the catalytic versatility of NzeB, as well as new insights into variables that control selectivity of CYP450 diketopiperazine dimerases.
•We propose a data-driven framework to analyze cerebro-spinal fMRI signals.•This approach disentangles activity into well-delineated, functionally relevant signatures.•We demonstrate its potential in ...the context of motor sequence learning.•We uncover cerebral and spinal networks that can be used to accurately decode learning stages.•This versatile approach can be readily extended to other facets of human behavior.
Mapping the neural patterns that drive human behavior is a key challenge in neuroscience. Even the simplest of our everyday actions stem from the dynamic and complex interplay of multiple neural structures across the central nervous system (CNS). Yet, most neuroimaging research has focused on investigating cerebral mechanisms, while the way the spinal cord accompanies the brain in shaping human behavior has been largely overlooked. Although the recent advent of functional magnetic resonance imaging (fMRI) sequences that can simultaneously target the brain and spinal cord has opened up new avenues for studying these mechanisms at multiple levels of the CNS, research to date has been limited to inferential univariate techniques that cannot fully unveil the intricacies of the underlying neural states. To address this, we propose to go beyond traditional analyses and instead use a data-driven multivariate approach leveraging the dynamic content of cerebro-spinal signals using innovation-driven coactivation patterns (iCAPs). We demonstrate the relevance of this approach in a simultaneous brain-spinal cord fMRI dataset acquired during motor sequence learning (MSL), to highlight how large-scale CNS plasticity underpins rapid improvements in early skill acquisition and slower consolidation after extended practice. Specifically, we uncovered cortical, subcortical and spinal functional networks, which were used to decode the different stages of learning with a high accuracy and, thus, delineate meaningful cerebro-spinal signatures of learning progression. Our results provide compelling evidence that the dynamics of neural signals, paired with a data-driven approach, can be used to disentangle the modular organization of the CNS. While we outline the potential of this framework to probe the neural correlates of motor learning, its versatility makes it broadly applicable to explore the functioning of cerebro-spinal networks in other experimental or pathological conditions.
•The current evidence suggests that patients treated with dorsal distraction plating for distal radius fractures regain 48° of flexion and 51° of extension. Furthermore, patients were able to achieve ...76° of supination and 74° of pronation. Grip strength was found to be 80% compared to the contralateral, uninjured limb.•Radiographic outcomes of distal radius fractures treated with dorsal distraction plating are also comparable to those treated with volar plate fixation. Patients treated with dorsal distraction plating have a restoration in their normal distal radius radiographic parameters with a mean volar tilt of 4.8°, radial height of 10.5 mm, radial inclination of 19.4° and ulnar variance of 0.3 mm. The current body of evidence analyzing radiographic outcomes following volar plate fixation show similar measurements to this.•Complication rates of dorsal plating are exceedingly low. Reported infection rates of dorsal plating has been quoted to be 1.6% compared to 52%–63% seen with external fixation and 3.7% seen with volar plate fixation. Other complications such as extensor tendon rupture, adhesions, and extensor lag are also low.
Optimal fixation for highly comminuted distal radius fractures remains a major treatment challenge for orthopaedic surgeons. Dorsal distraction plating can serve as an improved fixation technique by allowing reduction under ligamentotaxis, providing a dorsal buttress, addressing proximal comminution, and allowing for early weightbearing in polytrauma patients. The aim of this study was to review current literature regarding treatment of distal radius fractures treated with dorsal distraction plating.
We performed a literature search in Pubmed and EMBASE databases to identify all studies analyzing use of dorsal distraction plating. Case reports, biomechanical and anatomic cadaver studies were excluded from analysis. Primary outcome measures were range of motion (ROM) at final follow up, grip strength, and radiographic parameters.
Eight studies were included in the final analysis. Pooled mean ROM after dorsal distraction plating was found to be 47.6° of flexion, 50.5° of extension, 76.0° of pronation, and 74.2° of supination. Pooled mean grip strength was 79.1% compared to the uninjured contralateral limb. Pooled mean volar tilt was 3.6°. Overall radial height was maintained at an average of 10.5 mm with a pooled mean loss of only 3.8 mm in length. Mean radial inclination was found to be 19.4 mm with patients having a mean ulnar variance of 0.5 mm.
Treatment of comminuted intra-articular distal radius fractures with dorsal distraction plating yielded excellent outcomes with very low complication rates, and has several advantages over volar plating and/or external fixation for these fractures. Necessity of plate removal remains a negative feature of this technique.
To assess the relationship between the presence of REM sleep behavior disorder (RBD) and the cognitive profile of nondemented patients with Parkinson disease (PD).
Cognitive impairment is an ...important nonmotor symptom in PD. Waking EEG slowing in nondemented PD has been related to the presence of RBD, a parasomnia affecting brainstem structures and frequently reported in PD. For this reason, RBD may be associated with cognitive impairment in PD.
Thirty-four patients with PD (18 patients with polysomnographic-confirmed RBD and 16 patients without RBD) and 25 healthy control subjects matched for age and educational level underwent sleep laboratory recordings and a comprehensive neuropsychological assessment.
Patients with PD and concomitant RBD showed significantly poorer performance on standardized tests measuring episodic verbal memory, executive functions, as well as visuospatial and visuoperceptual processing compared to both patients with PD without RBD and control subjects. Patients with PD without RBD had no detectable cognitive impairment compared to controls.
This study shows that cognitive impairment in nondemented patients with Parkinson disease (PD) is closely related to the presence of REM sleep behavior disorder, a sleep disturbance that was not controlled for in previous studies assessing cognitive deficits in PD.
Consciousness is reduced during nonrapid eye movement (NREM) sleep due to changes in brain function that are still poorly understood. Here, we tested the hypothesis that impaired consciousness during ...NREM sleep is associated with an increased modularity of brain activity. Cerebral connectivity was quantified in resting-state functional magnetic resonance imaging times series acquired in 13 healthy volunteers during wakefulness and NREM sleep. The analysis revealed a modification of the hierarchical organization of large-scale networks into smaller independent modules during NREM sleep, independently from EEG markers of the slow oscillation. Such modifications in brain connectivity, possibly driven by sleep ultraslow oscillations, could hinder the brain's ability to integrate information and account for decreased consciousness during NREM sleep.
•Three months of aerobic exercise training (AET) improves fitness in PD patients.•Effects of AET on cognitive and motor skills in PD were evaluated concurrently.•Some executive functions and ...procedural learning capacity improved after AET.•AET can be used as a non-pharmacological intervention to improve functioning in PD.
Background: Aerobic exercise training (AET) has been shown to provide health benefits in individuals with Parkinson’s disease (PD). However, it is yet unknown to what extent AET also improves cognitive and procedural learning capacities, which ensure an optimal daily functioning. Objective: In the current study, we assessed the effects of a 3-month AET program on executive functions (EF), implicit motor sequence learning (MSL) capacity, as well as on different health-related outcome indicators. Methods: Twenty healthy controls (HC) and 19 early PD individuals participated in a supervised, high-intensity, stationary recumbent bike-training program (3 times/week for 12weeks). Exercise prescription started at 20min (+5min/week up to 40min) based on participant’s maximal aerobic power. Before and after AET, EF tests assessed participants’ inhibition and flexibility functions, whereas implicit MSL capacity was evaluated using a version of the Serial Reaction Time Task. Results: The AET program was effective as indicated by significant improvement in aerobic capacity in all participants. Most importantly, AET improved inhibition but not flexibility, and motor learning skill, in both groups. Conclusion: Our results suggest that AET can be a valuable non-pharmacological intervention to promote physical fitness in early PD, but also better cognitive and procedural functioning.
This study aimed to determine the distinct contribution of slow (11–13
Hz) and fast (13–15
Hz) spindles in the consolidation process of a motor sequence learning task (MSL). Young subjects (
n
=
12) ...were trained on both a finger MSL task and a control (CTRL) condition, which were administered one week apart in a counterbalanced order. Subjects were asked to practice the MSL or CTRL task in the evening (approximately 9:00
p.m.) and their performance was retested on the same task 12
h later (approximately 9:00
a.m.). Polysomnographic (PSG) recordings were performed during the night following training on either task, and an automatic algorithm was used to detect fast and slow spindles and to quantify their characteristics (i.e., density, amplitude, and duration). Statistical analyses revealed higher fast (but not slow) spindle density after training on the MSL than after practice of the CTRL task. The increase in fast spindle density on the MSL task correlated positively with overnight performance gains on the MSL task and with difference in performance gain between the MSL and CTRL tasks. Together, these results suggest that fast sleep spindles help activate the cerebral network involved in overnight MSL consolidation, while slow spindles do not appear to play a role in this mnemonic process.
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