skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: Anti-Arrhenius behavior of electron transfer reactions in molecular dimers
The degree of torsional hindrance can significantly contribute to anti-Arrhenius behavior of charge recombination, wherein recombination rates decrease as temperature increases.  more » « less
Award ID(s):
2144787
PAR ID:
10483346
Author(s) / Creator(s):
;
Publisher / Repository:
Royal Society of Chemistry
Date Published:
Journal Name:
Chemical Science
Volume:
14
Issue:
45
ISSN:
2041-6520
Page Range / eLocation ID:
13095 to 13107
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Josephs, Emily (Ed.)
    Abstract Meiotic recombination is an integral cellular process, required for the production of viable gametes. Recombination rate is a fundamental genomic parameter, modulating genomic responses to selection. Our increasingly detailed understanding of its molecular underpinnings raises the prospect that we can gain insight into trait divergence by examining the molecular evolution of recombination genes from a pathway perspective, as in mammals, where protein-coding changes in later stages of the recombination pathway are connected to divergence in intra-clade recombination rate. Here, we leverage increased availability of avian and teleost genomes to reconstruct the evolution of the recombination pathway across two additional vertebrate clades: birds, which have higher and more variable rates of recombination and similar divergence times to mammals, and teleost fish, which have much deeper divergence times. Rates of molecular evolution of recombination genes are highly correlated between vertebrate clades and significantly elevated compared to control panels, suggesting that they experience similar selective pressures. Avian recombination genes are significantly more likely to exhibit signatures of positive selection than other clades, unrestricted to later stages of the pathway. Signatures of positive selection in genes linked to recombination rate variation in mammalian populations and those with signatures of positive selection across the avian phylogeny are highly correlated. In contrast, teleost fish recombination genes have significantly less evidence of positive selection despite high intra-clade recombination rate variability. Gaining clade-specific understanding of patterns of variation in recombination genes can elucidate drivers of recombination rate and thus, factors influencing genetic diversity, selection efficacy, and species divergence. 
    more » « less
  2. Blanco-Melo, Daniel (Ed.)
    Coronavirus genomes have evolutionary histories shaped extensively by recombination. Yet, how often recombination occurs at a cellular level, or the factors that regulate recombination rates, are poorly understood. Utilizing experimental co-infections with pairs of genetically distinct coronaviruses, we found that recombination is both frequent and rare during coinfection. Recombination occurred in every instance of co-infection yet resulted in relatively few recombinant RNAs. By integrating a discrete-time Susceptible-Infected-Removed (SIR) model, we found that rates of recombination are determined primarily by rates of cellular co-infection, rather than other possible barriers such as RNA compartmentalization. By staggering the order and timing of infection with each virus we also found that rates of co-infection are themselves heavily influenced by genetic and ecological mechanisms, including superinfection exclusion and the relative fitness of competing viruses. Our study highlights recombination as a potent yet regulated force: frequent enough to ensure a steady influx of genetic variation but also infrequent enough to maintain genomic integrity. As recombination is thought to be an important driver of host-switching and disease emergence, our study provides new insights into the factors that regulate coronavirus recombination and evolution more broadly. 
    more » « less
  3. Meiotic recombination between homologous chromosomes is vital for maximizing genetic variation among offspring. However, sex-determining regions are often rearranged and blocked from recombination. It remains unclear whether rearrangements or other mechanisms might be responsible for recombination suppression. Here, we uncover that the deficiency of the DNA cytosine methyltransferase DNMT1 in the green algaChlamydomonas reinhardtiicauses anomalous meiotic recombination at the mating-type locus (MT), generating haploid progeny containing bothplusandminusmating-type markers due to crossovers withinMT. The deficiency of a histone methyltransferase for H3K9 methylation does not lead to anomalous recombination. These findings suggest that DNA methylation, rather than rearrangements or histone methylation, suppresses meiotic recombination, revealing an unappreciated biological function for DNA methylation in eukaryotes. 
    more » « less
  4. Meiotic recombination rates vary in response to intrinsic and extrinsic factors. Recently, heat stress has been shown to reveal plasticity in recombination rates in Drosophila pseudoobscura. Here, a combination of molecular genotyping and X-linked recessive phenotypic markers were used to investigate differences in recombination rates due to heat stress. In addition, haplotypes from the genetic crosses were compared to test if they deviated from equal proportions, which would indicate viability selection. To avoid this potential bias, SNP genotyping markers overlapping the regions assayed with mutant markers were used to further investigate recombination rate. Interestingly, skews in haplotype frequency were consistent with the fixation of alleles in the wild-type stocks used that are unfit at high temperature. Evidence of viability selection due to heat stress in the wild-type haplotypes was most apparent on days 7–9 when more mutant non-crossover haplotypes were recovered in comparison to wild type (p < 0.0001). Recombination analysis using SNP markers showed days 9–10 as significantly different due to heat stress in 2 pairs of consecutive SNP markers (p = 0.018; p = 0.015), suggesting that during this time period the recombination rate is most sensitive to heat stress. This peak timing for recombination plasticity is consistent with Drosophila melanogaster based on a comparison of similarly timed key meiotic events, enabling future mechanistic work of temperature stress on recombination rate. 
    more » « less
  5. Understanding carrier recombination processes in metal halide perovskites is fundamentally important to further improving the efficiency of perovskite solar cells, yet the accurate recombination velocity at grain boundaries (GBs) has not been determined. Here, we report the determination of carrier recombination velocities at GBs (SGB) of polycrystalline perovskites by mapping the transient photoluminescence pattern change induced by the nonradiative recombination of carriers at GBs. Charge recombination at GBs is revealed to be even stronger than at surfaces of unpassivated films, with averageSGBreaching 2200 to 3300 cm/s. Regular surface treatments do not passivate GBs because of the absence of contact at GBs. We find a surface treatment using tributyl(methyl)phosphonium dimethyl phosphate that can penetrate into GBs by partially dissolving GBs and converting it into one-dimensional perovskites. It reduces the averageSGBby four times, with the lowestSGBof 410 cm/s, which is comparable to surface recombination velocities after passivation. 
    more » « less