The conserved ATPase, PCH-2/TRIP13, is required during both the spindle checkpoint and meiotic prophase. However, its specific role in regulating meiotic homolog pairing, synapsis and recombination has been enigmatic. Here, we report that this enzyme is required to proofread meiotic homolog interactions. We generated a mutant version of PCH-2 in C . elegans that binds ATP but cannot hydrolyze it: pch-2 E253Q . In vitro , this mutant can bind a known substrate but is unable to remodel it. This mutation results in some non-homologous synapsis and impaired crossover assurance. Surprisingly, worms with a null mutation in PCH-2’s adapter protein, CMT-1, the ortholog of p31 comet , localize PCH-2 to meiotic chromosomes, exhibit non-homologous synapsis and lose crossover assurance. The similarity in phenotypes between cmt-1 and pch-2 E253Q mutants suggest that PCH-2 can bind its meiotic substrates in the absence of CMT-1, in contrast to its role during the spindle checkpoint, but requires its adapter to hydrolyze ATP and remodel them.

Charge mobility of crystalline organic semiconductors (OSC) is limited by local dynamic disorder. Recently, the charge mobility for several high mobility OSCs, including TIPS-pentacene, were accurately predicted from a density functional theory (DFT) simulation constrained by the crystal structure and the inelastic neutron scattering spectrum, which provide direct measures of the structure and the dynamic disorder in the length scale and energy range of interest. However, the computational expense required for calculating all of the atomic and molecular forces is prohibitive. Here we demonstrate the use of density functional tight binding (DFTB), a semiempirical quantum mechanical method that is 2 to 3 orders of magnitude more efficient than DFT. We show that force matching a many-body interaction potential to DFT derived forces yields highly accurate DFTB models capable of reproducing the low-frequency intricacies of experimental inelastic neutron scattering (INS) spectra and accurately predicting charge mobility. We subsequently predicted charge mobilities from our DFTB model of a number of previously unstudied structural analogues to TIPS-pentacene using dynamic disorder from DFTB and transient localization theory. The approach we establish here could provide a truly rapid simulation pathway for accurate materials properties prediction, in our vision applied to new OSCs with tailored properties.

Knowledge of the full phonon spectrum is essential to accurately calculate the dynamic disorder (σ) and hole mobility (μ h ) in organic semiconductors (OSCs). However, most vibrational spectroscopy techniques under-measure the phonons, thus limiting the phonon validation. Here, we measure and model the full phonon spectrum using multiple spectroscopic techniques and predict μ h using σ from only the Γ-point and the full Brillouin zone (FBZ). We find that only inelastic neutron scattering (INS) provides validation of all phonon modes, and that σ in a set of small molecule semiconductors can be miscalculated by up to 28% when comparing Γ-point against FBZ calculations. A subsequent mode analysis shows that many modes contribute to σ and that no single mode dominates. Our results demonstrate the importance of a thoroughly validated phonon calculation, and a need to develop design rules considering the full spectrum of phonon modes.

Atomic vibrations can inform about materials properties from hole transport in organic semiconductors to correlated disorder in metal−organic frameworks. Currently, there are several methods for predicting these vibrations using simulations, but the accuracy−efficiency tradeoffs have not been examined in depth. In this study, rubrene is used as a model system to predict atomic vibrational properties using six different simulation methods: density functional theory, density functional tight binding, density functional tight binding with a Chebyshev polynomial-based correction, a trained machine learning model, a pretrained machine learning model called ANI-1, and a classical forcefield model. The accuracy of each method is evaluated by comparison to the experimental inelastic neutron scattering spectrum. All methods discussed here show some accuracy across a wide energy region, though the Chebyshev-corrected tight-binding method showed the optimal combination of high accuracy with low expense. We then offer broad simulation guidelines to yield efficient, accurate results for inelastic neutron scattering spectrum prediction.

Every material experiences atomic and molecular motions that are generally termed vibrations in gases and liquids or phonons in solid state materials. Optical spectroscopy techniques, such as Raman, infrared absorption spectroscopy, or inelastic neutron scattering (INS), can be used to measure the vibrational/phonon spectrum of ground state materials properties. A variety of optical pump probe spectroscopies enable the measurement of excited states or elucidate photochemical reaction pathways and kinetics. So far, it has not been possible to study photoactive materials or processes in situ using INS due to the mismatch between neutron and photon penetration depths, differences between the flux density of photons and neutrons, cryogenic temperatures for INS measurements, vacuum conditions, and a lack of optical access to the sample space. These experimental hurdles have resulted in very limited photochemistry studies using INS. Here we report on the design of two different photochemistry sample sticks that overcome these experimental hurdles to enable in situ photochemical studies using INS, specifically at the VISION instrument at Oak Ridge National Laboratory. We demonstrate the use of these new measurement capabilities through (1) the in situ photodimerization of anthracene and (2) the in situ photopolymerization of a 405 nm photoresin using 405 nm excitation as simple test cases. These new measurement apparatus broaden the science enabled by INS to include photoactive materials, optically excited states, and photoinitiated reactions.

18 19 The conserved ATPase, PCH-2/TRIP13, is required during both the spindle checkpoint and 20 meiotic prophase. However, it's specific role in regulating meiotic homolog pairing, synapsis and 21 recombination has been enigmatic. Here, we report that this enzyme is required to proofread 22 meiotic homolog interactions. We generated a mutant version of PCH-2 in C. elegans that binds 23 ATP but cannot hydrolyze it: pch-2 E253Q . In vitro, this mutant binds its substrates but is unable to 24 remodel them. This mutation results in non-homologous synapsis and loss of crossover 25 assurance. Surprisingly, worms with a null mutation in PCH-2's adapter protein, CMT-1, the 26 ortholog of p31 comet , localize PCH-2 to meiotic chromosomes, exhibit non-homologous synapsis 27 and lose crossover assurance. The similarity in phenotypes between cmt-1 and pch-2 E253Q 28 mutants indicate that PCH-2 can bind its meiotic substrates in the absence of in 29 contrast to its role during the spindle checkpoint, but requires its adapter to hydrolyze ATP and 30 remodel them. 31Introduction 32 33 Sexual reproduction relies on meiosis, the specialized cell division that generates haploid 34 gametes, such as sperm and eggs, from diploid progenitors so that fertilization restores diploidy. 35To ensure that gametes inherit the correct number of chromosomes, meiotic chromosome 36 segregation is exquisitely choreographed: Homologous chromosomes segregate in meiosis I 37 and sister chromatids segregate in meiosis II. Having an incorrect number of chromosomes, 38 also called aneuploidy, is associated with infertility, miscarriages and birth defects, underscoring 39 the importance of understanding this process to human health. 40 41 Events in meiotic prophase ensure proper chromosome segregation. During prophase, 42 homologous chromosomes undergo progressively intimate interactions that culminate in 43 synapsis and crossover recombination (reviewed in [1]). After homologs pair, a macromolecular 44 complex, called the synaptonemal complex (SC), is assembled between them in a process 45 called synapsis. Synapsis is a prerequisite for crossover recombination to generate the 46 linkages, or chiasmata, between homologous chromosomes that direct meiotic chromosome 47 segregation. Defects in any of these events can result in chromosome missegregation during 48 the meiotic divisions and gametes, and therefore embryos, with an incorrect number of 49 chromosomes. 50 51The conserved AAA-ATPase PCH-2 (Pch2 in budding yeast, PCH2 in Arabidopsis and TRIP13 52 in mice) is crucial to coordinate these events in meiotic prophase. In vitro and cytological 53 experiments indicate that it does this by using the energy of ATP hydrolysis to remodel meiotic 54HORMADs [2][3][4][5][6], chromosomal proteins that are essential for pairing, synapsis, recombination 55 and checkpoint function [7][8][9][10][11][12][13][14][15][16][17][18]. HORMADs are a protein family defined by the ability of a 56 domain, the HORMA domain, to adopt multiple conformations that specify pr...

Patterned semiconductors are essential for the fabrication of nearly all electronic devices. Over the last two decades, semiconducting polymers (SPs) have received enormous attention due to their potential for creating low‐cost flexible electronic devices, while development of scalable patterning methods capable of producing sub‐μm feature sizes has lagged. A novel method for patterning SPs termed Projection Photothermal Lithography (PPL) is presented. A lab scale PPL microscope is built and it is demonstrated that rapid (≈4 cm2 h−1) and large single exposure area (≈0.69 mm2) sub‐μm patterns can be obtained optically. Polymer domains are selectively removed via a photo‐induced temperature gradient that enables dissolution. It is hypothesized that commercial‐scale patterning with a throughput of ≈5 m2 h−1 and resolution of <1 μm could be realized through optimization of optical components.