Influence of white and gray matter connections on endogenous human cortical oscillations

Brain oscillations reflect changes in electrical potentials summated across neuronal populations. Low- and high-frequency rhythms have different modulation patterns. Slower rhythms are spatially broad, while faster rhythms are more local. From this observation, we hypothesized that low- and high-frequency oscillations reflect white- and gray-matter communications, respectively, and synchronization between low-frequency phase with high-frequency amplitude represents a mechanism enabling distributed brain-networks to coordinate local processing. Testing this common understanding, we selectively disrupted white or gray matter connections to human cortex while recording surface field potentials. Counter to our original hypotheses, we found that cortex consists of independent oscillatory-units (IOUs) that maintain their own complex endogenous rhythm structure. IOUs are differentially modulated by white and gray matter connections. White-matter connections maintain topographical anatomic heterogeneity (i.e., separable processing in cortical space) and gray-matter connections segregate cortical synchronization patterns (i.e., separable temporal processing through phase-power coupling). Modulation of distinct oscillatory modules enables the functional diversity necessary for complex processing in the human brain

Comparing serial X-ray crystallography and microcrystal electron diffraction (MicroED) as methods for routine structure determination from small macromolecular crystals.

Innovative new crystallographic methods are facilitating structural studies from ever smaller crystals of biological macromolecules. In particular, serial X-ray crystallography and microcrystal electron diffraction (MicroED) have emerged as useful methods for obtaining structural information from crystals on the nanometre to micrometre scale. Despite the utility of these methods, their implementation can often be difficult, as they present many challenges that are not encountered in traditional macromolecular crystallography experiments. Here, XFEL serial crystallography experiments and MicroED experiments using batch-grown microcrystals of the enzyme cyclophilin A are described. The results provide a roadmap for researchers hoping to design macromolecular microcrystallography experiments, and they highlight the strengths and weaknesses of the two methods. Specifically, we focus on how the different physical conditions imposed by the sample-preparation and delivery methods required for each type of experiment affect the crystal structure of the enzyme

Mapping protein dynamics at high spatial resolution with temperature-jump X-ray crystallography

温度による酵素の構造変化を分子動画撮影 様々な生体高分子のダイナミクスを決定する新たな方法論. 京都大学プレスリリース. 2023-09-19.Understanding and controlling protein motion at atomic resolution is a hallmark challenge for structural biologists and protein engineers because conformational dynamics are essential for complex functions such as enzyme catalysis and allosteric regulation. Time-resolved crystallography offers a window into protein motions, yet without a universal perturbation to initiate conformational changes the method has been limited in scope. Here we couple a solvent-based temperature jump with time-resolved crystallography to visualize structural motions in lysozyme, a dynamic enzyme. We observed widespread atomic vibrations on the nanosecond timescale, which evolve on the submillisecond timescale into localized structural fluctuations that are coupled to the active site. An orthogonal perturbation to the enzyme, inhibitor binding, altered these dynamics by blocking key motions that allow energy to dissipate from vibrations into functional movements linked to the catalytic cycle. Because temperature jump is a universal method for perturbing molecular motion, the method demonstrated here is broadly applicable for studying protein dynamics

The Effect of Technological Improvement on Capacity

We formulate a model of capacity expansion that is relevant to a service provider for whom the cost of capacity shortages would be considerable but difficult to quantify exactly. Due to demand uncertainty and a lead time for adding capacity, not all shortages are avoidable. In addition, technological innovations will reduce the cost of adding capacity but may not be completely predictable. Analytical expressions for the infinite horizon expansion cost and shortages are optimized numerically. Sensitivity analyses allow us to determine the impact of technological change on the optimal timing and sizes of capacity expansions to account for economies of scale, the time value of money and penalties for insufficient capacity

Halochromic Isoquinoline with Mechanochromic Triphenylamine: Smart Fluorescent Material for Rewritable and Self-Erasable Fluorescent Platform

Halochromic isoquinoline attached mechanochromic triphenylamine, <i>N</i>-phenyl-N-(4-(quinolin-2-yl)­phenyl)­benzenamine (PQPBA) and tris­(4-(quinolin-2-yl)­phenyl)­amine (TQPA), smart fluorescent materials exhibit thermo/mechanochromism and tunable solid state fluorescence and their unusual halochromic response in PMMA matrix have been used for fabricating rewritable and self-erasable fluorescent platforms. PQPBA and TQPA showed strong fluorescence in solution (Φ_f = 0.9290 (PQPBA) and 0.9160 (TQPA)) and moderate solid state fluorescence (Φ_f = 20 (PQPBA) and 17% (TQPA). Interestingly, they exhibited a rare temperature (0–100 °C) dependent positive fluorescence enhancement via activating radiative vibrational transition. The deaggregation of PQPBA and TQPA in PMMA polymer matrix lead to the enhancement of fluorescence intensity strongly and fabricated strong blue fluorescent thin films (Φ_<i>f</i> = 58% (PQPBA) and 54% (TQPA). The halochromic isoquinoline has been exploited for demonstrating reversible off-on fluorescence switching by acid (TFA (trifluoroacetic acid)/HCl) and base (NH₃) treatment in both solids as well as PMMA thin films. Importantly, rewritable and self-erasable fluorescent platform has been achieved by make use of unusual fluorescence responses of PQPBA/TQPA with TFA/HCl after exposing NH₃. Single crystal and powder X-ray diffraction (PXRD) studies provided the insight on the solid-state fluorescence and external stimuli-induced fluorescence changes