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The Femtosecond X-ray Experiments (FXE) instrument at the European X-ray Free-Electron Laser (EuXFEL) provides an optimized platform for investigations of ultrafast physical, chemical and biological processes. It operates in the energy range 4.7-20 keVaccommodating flexible and versatile environments for a wide range of samples using diverse ultrafast X-ray spectroscopic, scattering and diffraction techniques. FXE is particularly suitable for experiments taking advantage of the sub-MHz repetition rates provided by the EuXFEL. In this paper a dedicated setup for studies on ultrafast biological and chemical dynamics in solution phase at sub-MHz rates at FXE is presented. Particular emphasis on the different liquid jet sample delivery options and their performance is given. Our portfolio of high-speed jets compatible with sub- MHz experiments includes cylindrical jets, gas dynamic virtual nozzles and flat jets. The capability to perform multi-color X-ray emission spectroscopy (XES) experiments is illustrated by a set of measurements using the dispersive X-ray spectrometer in von Hamos geometry. Static XES data collected using a multicrystal scanning Johann-type spectrometer are also presented. A few examples of experimental results on ultrafast time-resolved X-ray emission spectroscopy and wide-angle X-ray scattering at sub-MHz pulse repetition rates are given. [ABSTRACT FROM AUTHOR]

Highly charged iron ([Fe.sub.16+], here referred to as Fe XVII) produces some of the brightest X-ray emission lines from hot astrophysical objects (1), including galaxy clusters and stellar coronae, and [...]

Abstract Risks associated with HIV are well documented in research literature. Although a great deal has been written about high-risk sex, little research has been conducted to examine how young men who have sex with men (YMSM) perceive and define high-risk sexual behavior. In this study, we compare the 'professional' and 'folk' models of HIV risk based on YMSM's understanding of high-risk sex and where and how they gathered their understanding of HIV risk behaviors. The findings reported here emerged from the quantitative and qualitative interviews from the Healthy Young Men's Study, a longitudinal study examining risk and protective factors for substance use and sexual risk among an ethnically diverse sample of YMSM. Findings are discussed in relation to framing how service providers and others can increase YMSM's knowledge of sexual behavior and help them build solid foundations of sexual health education to protect them from sexually transmitted infections and HIV. [ABSTRACT FROM AUTHOR]

Young men who have sex with men (YMSM) face myriad challenges when deciding to disclose their sexual orientation to family members. Key to this decision is consideration of how disclosure may influence the support they receive from family. This paper explores a diverse sample of YMSM's (N = 43) perspectives on disclosure of their same-sex attractions to key family members and its impact on family support. Several stages/categories of disclosure are described and some YMSM seemed to continue to move between categories. Additionally, relationships after disclosure included negotiations between the expression of their sexual orientation and the maintenance of family support. [ABSTRACT FROM AUTHOR]

The 5'-3' exoribonuclease Xrn2, known as Rat1 in yeasts, terminates mRNA transcription by RNA polymerase II (RNAPII). In the torpedo model of termination, the activity of Xrn2/Rat1 is enhanced by Rai1, which is recruited to the termination site by Rtt103, an adaptor protein binding to the RNAPII C-terminal domain (CTD). The overall architecture of the Xrn2/Rat1-Rai1-Rtt103 complex remains unknown. We combined structural biology methods to characterize the torpedo complex from Saccharomyces cerevisiae and Chaetomium thermophilum. Comparison of the structures from these organisms revealed a conserved protein core fold of the subunits, but significant variability in their interaction interfaces. We found that in the mesophile, Rtt103 utilizes an unstructured region to augment a Rai1 β-sheet, while in the thermophile Rtt103 binds to a C-terminal helix of Rai1 via its CTD-interacting domain with an α-helical fold. These different torpedo complex assemblies reflect adaptations to the environment and impact complex recruitment to RNAPII., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Effective photoinduced charge transfer makes molecular bimetallic assemblies attractive for applications as active light-induced proton reduction systems. Developing competitive base metal dyads is mandatory for a more sustainable future. However, the electron transfer mechanisms from the photosensitizer to the proton reduction catalyst in base metal dyads remain so far unexplored. A Fe─Co dyad that exhibits photocatalytic H 2 production activity is studied using femtosecond X-ray emission spectroscopy, complemented by ultrafast optical spectroscopy and theoretical time-dependent DFT calculations, to understand the electronic and structural dynamics after photoexcitation and during the subsequent charge transfer process from the Fe II photosensitizer to the cobaloxime catalyst. This novel approach enables the simultaneous measurement of the transient X-ray emission at the iron and cobalt K-edges in a two-color experiment. With this methodology, the excited state dynamics are correlated to the electron transfer processes, and evidence of the Fe→Co electron transfer as an initial step of proton reduction activity is unraveled., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Metalloporphyrins with open d-shell ions can drive biochemical energy cycles. However, their utilization in photoconversion is hampered by rapid deactivation. Mapping the relaxation pathways is essential for elaborating strategies that can favorably alter the charge dynamics through chemical design and photoexcitation conditions. Here, we combine transient optical absorption spectroscopy and transient X-ray emission spectroscopy with femtosecond resolution to probe directly the coupled electronic and spin dynamics within a photoexcited nickel porphyrin in solution. Measurements and calculations reveal that a state with charge-transfer character mediates the formation of the thermalized excited state, thereby advancing the description of the photocycle for this important representative molecule. More generally, establishing that intramolecular charge-transfer steps play a role in the photoinduced dynamics of metalloporphyrins with open d-shell sets a conceptual ground for their development as building blocks capable of boosting nonadiabatic photoconversion in functional architectures through "hot" charge transfer down to the attosecond time scale.

Biomolecular polyelectrolyte complexes can be formed between oppositely charged intrinsically disordered regions (IDRs) of proteins or between IDRs and nucleic acids. Highly charged IDRs are abundant in the nucleus, yet few have been functionally characterized. Here, we show that a positively charged IDR within the human ATP-dependent DNA helicase Q4 (RECQ4) forms coacervates with G-quadruplexes (G4s). We describe a three-step model of charge-driven coacervation by integrating equilibrium and kinetic binding data in a global numerical model. The oppositely charged IDR and G4 molecules form a complex in the solution that follows a rapid nucleation-growth mechanism leading to a dynamic equilibrium between dilute and condensed phases. We also discover a physical interaction with Replication Protein A (RPA) and demonstrate that the IDR can switch between the two extremes of the structural continuum of complexes. The structural, kinetic, and thermodynamic profile of its interactions revealed a dynamic disordered complex with nucleic acids and a static ordered complex with RPA protein. The two mutually exclusive binding modes suggest a regulatory role for the IDR in RECQ4 function by enabling molecular handoffs. Our study extends the functional repertoire of IDRs and demonstrates a role of polyelectrolyte complexes involved in G4 binding., (© 2023. Springer Nature Limited.)

RNase III Dicer produces small RNAs guiding sequence-specific regulations, with important biological roles in eukaryotes. Major Dicer-dependent mechanisms are RNA interference (RNAi) and microRNA (miRNA) pathways, which employ distinct types of small RNAs. Small interfering RNAs (siRNAs) for RNAi are produced by Dicer from long double-stranded RNA (dsRNA) as a pool of different small RNAs. In contrast, miRNAs have specific sequences because they are precisely cleaved out from small hairpin precursors. Some Dicer homologs efficiently generate both, siRNAs and miRNAs, while others are adapted for biogenesis of one small RNA type. Here, we review the wealth of recent structural analyses of animal and plant Dicers, which have revealed how different domains and their adaptations contribute to substrate recognition and cleavage in different organisms and pathways. These data imply that siRNA generation was Dicer's ancestral role and that miRNA biogenesis relies on derived features. While the key element of functional divergence is a RIG-I-like helicase domain, Dicer-mediated small RNA biogenesis also documents the impressive functional versatility of the dsRNA-binding domain., (© 2023 The Authors. Published under the terms of the CC BY 4.0 license.)

X-ray free-electron laser sources enable time-resolved X-ray studies with unmatched temporal resolution. To fully exploit ultrashort X-ray pulses, timing tools are essential. However, new high repetition rate X-ray facilities present challenges for currently used timing tool schemes. Here we address this issue by demonstrating a sensitive timing tool scheme to enhance experimental time resolution in pump-probe experiments at very high pulse repetition rates. Our method employs a self-referenced detection scheme using a time-sheared chirped optical pulse traversing an X-ray stimulated diamond plate. By formulating an effective medium theory, we confirm subtle refractive index changes, induced by sub-milli-Joule intense X-ray pulses, that are measured in our experiment. The system utilizes a Common-Path-Interferometer to detect X-ray-induced phase shifts of the optical probe pulse transmitted through the diamond sample. Owing to the thermal stability of diamond, our approach is well-suited for MHz pulse repetition rates in superconducting linear accelerator-based free-electron lasers., (© 2023. The Author(s).)

We report femtosecond Fe K-edge absorption (XAS) and nonresonant X-ray emission (XES) spectra of ferric cytochrome C (Cyt c) upon excitation of the haem (>300 nm) or mixed excitation of the haem and tryptophan (<300 nm). The XAS and XES transients obtained in both excitation energy ranges show no evidence for electron transfer processes between photoexcited tryptophan (Trp) and the haem, but rather an ultrafast energy transfer, in agreement with previous ultrafast optical fluorescence and transient absorption studies. The reported ( J. Phys. Chem. B 2011 , 115 (46), 13723-13730) decay times of Trp fluorescence in ferrous (∼350 fs) and ferric (∼700 fs) Cyt c are among the shortest ever reported for Trp in a protein. The observed time scales cannot be rationalized in terms of Förster or Dexter energy transfer mechanisms and call for a more thorough theoretical investigation.

Electron transfer reactions can be strongly influenced by solvent dynamics. We study the photoionization of halides in water as a model system for such reactions. There are no internal nuclear degrees of freedom in the solute, allowing the dynamics of the solvent to be uniquely identified. We simulate the equilibrium solvent dynamics for Cl - , Br - , I - , and their respective neutral atoms in water, comparing quantum mechanical/molecular mechanical (QM/MM) and classical molecular dynamics (MD) methods. On the basis of the obtained configurations, we calculate the extended X-ray absorption fine structure (EXAFS) spectra rigorously based on the MD snapshots and compare them in detail with other theoretical and experimental results available in the literature. We find our EXAFS spectra based on QM/MM MD simulations in good agreement with their experimental counterparts for the ions. Classical MD simulations for the ions lead to EXAFS spectra that agree equally well with the experiment when it comes to the oscillatory period of the signal, even though they differ from the QM/MM radial distribution functions extracted from the MD. The amplitude is, however, considerably overestimated. This suggests that to judge the reliability of theoretical simulation methods or to elucidate fine details of the atomistic dynamics of the solvent based on EXAFS spectra, the amplitude as well as the oscillatory period need to be considered. If simulations fail qualitatively, as does the classical MD for the aqueous neutral halogen atoms, the resulting EXAFS will also be strongly affected in both oscillatory period and amplitude. The good reliability of QM/MM-based EXAFS simulations, together with clear qualitative differences in the EXAFS spectra found between halides and their atomic counterparts, suggests that a combined theory and experimental EXAFS approach is suitable for elucidating the nonequilibrium solvent dynamics in the photoionization of halides and possibly also for electron transfer reactions in more complex systems.

We present a sub-picosecond resolved investigation of the structural solvent reorganization and geminate recombination dynamics following 400 nm two-photon excitation and photodetachment of a valence p electron from the aqueous atomic solute, I - (aq). The measurements utilized time-resolved X-ray Absorption Near Edge Structure (TR-XANES) spectroscopy and X-ray Solution Scattering (TR-XSS) at the Linac Coherent Light Source x-ray free electron laser in a laser pump/x-ray probe experiment. The XANES measurements around the L 1 -edge of the generated nascent iodine atoms (I 0 ) yield an average electron ejection distance from the iodine parent of 7.4 ± 1.5 Å with an excitation yield of about 1/3 of the 0.1M NaI aqueous solution. The kinetic traces of the XANES measurement are in agreement with a purely diffusion-driven geminate iodine-electron recombination model without the need for a long-lived (I 0 :e - ) contact pair. Nonequilibrium classical molecular dynamics simulations indicate a delayed response of the caging H 2 O solvent shell and this is supported by the structural analysis of the XSS data: We identify a two-step process exhibiting a 0.1 ps delayed solvent shell reorganization time within the tight H-bond network and a 0.3 ps time constant for the mean iodine-oxygen distance changes. The results indicate that most of the reorganization can be explained classically by a transition from a hydrophilic cavity with a well-ordered first solvation shell (hydrogens pointing toward I - ) to an expanded cavity around I 0 with a more random orientation of the H 2 O molecules in a broadened first solvation shell.

MicroRNA (miRNA) and RNA interference (RNAi) pathways rely on small RNAs produced by Dicer endonucleases. Mammalian Dicer primarily supports the essential gene-regulating miRNA pathway, but how it is specifically adapted to miRNA biogenesis is unknown. We show that the adaptation entails a unique structural role of Dicer's DExD/H helicase domain. Although mice tolerate loss of its putative ATPase function, the complete absence of the domain is lethal because it assures high-fidelity miRNA biogenesis. Structures of murine Dicer•-miRNA precursor complexes revealed that the DExD/H domain has a helicase-unrelated structural function. It locks Dicer in a closed state, which facilitates miRNA precursor selection. Transition to a cleavage-competent open state is stimulated by Dicer-binding protein TARBP2. Absence of the DExD/H domain or its mutations unlocks the closed state, reduces substrate selectivity, and activates RNAi. Thus, the DExD/H domain structurally contributes to mammalian miRNA biogenesis and underlies mechanistical partitioning of miRNA and RNAi pathways., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

Transcription elongation factor Spt6 associates with RNA polymerase II (Pol II) and acts as a histone chaperone, which promotes the reassembly of nucleosomes following the passage of Pol II. The precise mechanism of nucleosome reassembly mediated by Spt6 remains unclear. In this study, we used a hybrid approach combining cryo-electron microscopy and small-angle X-ray scattering to visualize the architecture of Spt6 from Saccharomyces cerevisiae. The reconstructed overall architecture of Spt6 reveals not only the core of Spt6, but also its flexible N- and C-termini, which are critical for Spt6's function. We found that the acidic N-terminal region of Spt6 prevents the binding of Spt6 not only to the Pol II CTD and Pol II CTD-linker, but also to pre-formed intact nucleosomes and nucleosomal DNA. The N-terminal region of Spt6 self-associates with the tSH2 domain and the core of Spt6 and thus controls binding to Pol II and nucleosomes. Furthermore, we found that Spt6 promotes the assembly of nucleosomes in vitro. These data indicate that the cooperation between the intrinsically disordered and structured regions of Spt6 regulates nucleosome and Pol II CTD binding, and also nucleosome assembly., (© The Author(s) 2022. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Background: Species of Danionella rank among the smallest of all vertebrates and their miniature size is correlated with an extreme case of progenesis, resulting in tiny, transparent sexually mature individuals. Progenesis has affected the entire skeleton of Danionella, in which 60 skeletal elements are absent, including some of the skull roofing bones. This lack of a skull roof combined with the presence of a fully formed hearing and sound producing apparatus has led to Danionella being used as an important model for neurophysiological studies., Results: Using both rank based and PGi analyses we investigate sequence heterochrony in the development of the skeleton of Danionella dracula and close relatives. Extreme heterochronic shifts affect the appearance of bony elements in Danionella dracula. This includes a delay in the appearance of most chondral skull bones, and a reduction or loss of dermal bones that would otherwise form the skull roof. In contrast, formation of the anterior region of the vertebral column, including the functionally important elements of the Weberian apparatus, is greatly accelerated., Conclusions: Here we show that the anatomical conditions that favor Danionella for brain research are the result of extreme heterochronic shifts that have acted differentially across the skeleton., (© 2020 American Association of Anatomists.)

Young men who have sex with men (YMSM), especially YMSM of color, are at increased risk for a wide range of threats to their health and well-being. In this study, we recruited and surveyed an urban sample of 448 young African American/Black (Black), Hispanic/Latino (Latino), and multi-racial/ethnic YMSM, ages 16-24 years (mean = 22.3 years), about stressful life events, their health and mental health, their access to and utilization of care, and their involvement in risk-related behaviors. We found that the majority reported experiences of racism (87%) and homophobia (76%). A high percentage reported food insecurity/hunger (36%), residential instability (15%), financial hardship (63%), and conflict with family/friends (62%). The prevalence of risk behaviors was also high, including recent use of tobacco (46%), alcohol (88%), and marijuana (72%), and 41% tested positive for 1+ drugs. Furthermore, 26% tested positive for 1+ sexually transmitted infections (STIs). Over half (56%) reported being worried about their health, 33% reported having a chronic health condition and 31% a mental health condition, and 45% had wanted/needed mental health services during the past year. Further, 17% reported suicidal ideation/had planned a suicide attempt and 26% had ever engaged in self-injurious behaviors. Significant differences by race/ethnicity and HIV status included residential status/food insecurity, type of racism/homophobia, drug use, and STIs. These findings demonstrate how vulnerable this population is with respect to a wide range of structural and social determinants of health that may be important drivers of behavioral, health, mental health outcomes, and potentially long-term health disparities.

The structure-function relationship is at the heart of biology, and major protein deformations are correlated to specific functions. For ferrous heme proteins, doming is associated with the respiratory function in hemoglobin and myoglobins. Cytochrome c (Cyt c) has evolved to become an important electron-transfer protein in humans. In its ferrous form, it undergoes ligand release and doming upon photoexcitation, but its ferric form does not release the distal ligand, while the return to the ground state has been attributed to thermal relaxation. Here, by combining femtosecond Fe K α and K β X-ray emission spectroscopy (XES) with Fe K-edge X-ray absorption near-edge structure (XANES), we demonstrate that the photocycle of ferric Cyt c is entirely due to a cascade among excited spin states of the iron ion, causing the ferric heme to undergo doming, which we identify. We also argue that this pattern is common to a wide diversity of ferric heme proteins, raising the question of the biological relevance of doming in such proteins., Competing Interests: The authors declare no competing interest., (Copyright © 2020 the Author(s). Published by PNAS.)

Oligonuclear complexes of d 4 -d 7 transition metal ion centers that undergo spin-switching have long been developed for their practical role in molecular electronics. Recently, they also have appeared as promising photochemical reactants demonstrating improved stability. However, the lack of knowledge about their photophysical properties in the solution phase compared to mononuclear complexes is currently hampering their inclusion into advanced light-driven reactions. In the present study, the ultrafast photoinduced dynamics in a solvated [2 × 2] iron(II) metallogrid complex are characterized by combining measurements with transient optical-infrared absorption and x-ray emission spectroscopy on the femtosecond time scale. The analysis is supported by density functional theory calculations. The photocycle can be described in terms of intra-site transitions, where the Fe II centers in the low-spin state are independently photoexcited. The Franck-Condon state decays via the formation of a vibrationally hot high-spin (HS) state that displays coherent behavior within a few picoseconds and thermalizes within tens of picoseconds to yield a metastable HS state living for several hundreds of nanoseconds. Systematic comparison with the closely related mononuclear complex [Fe(terpy) 2 ] 2+ reveals that nuclearity has a profound impact on the photoinduced dynamics. More generally, this work provides guidelines for expanding the integration of oligonuclear complexes into new photoconversion schemes that may be triggered by ultrafast spin-switching.

Pervasive transcription is a widespread phenomenon leading to the production of a plethora of non-coding RNAs (ncRNAs) without apparent function. Pervasive transcription poses a threat to proper gene expression that needs to be controlled. In yeast, the highly conserved helicase Sen1 restricts pervasive transcription by inducing termination of non-coding transcription. However, the mechanisms underlying the specific function of Sen1 at ncRNAs are poorly understood. Here, we identify a motif in an intrinsically disordered region of Sen1 that mimics the phosphorylated carboxy-terminal domain (CTD) of RNA polymerase II, and structurally characterize its recognition by the CTD-interacting domain of Nrd1, an RNA-binding protein that binds specific sequences in ncRNAs. In addition, we show that Sen1-dependent termination strictly requires CTD recognition by the N-terminal domain of Sen1. We provide evidence that the Sen1-CTD interaction does not promote initial Sen1 recruitment, but rather enhances Sen1 capacity to induce the release of paused RNAPII from the DNA. Our results shed light on the network of protein-protein interactions that control termination of non-coding transcription by Sen1., (© 2020 The Authors. Published under the terms of the CC BY 4.0 license.)

An atomistic understanding of the photoinduced spin-state switching (PSS) within polynuclear systems of d 4 -d 7 transition metal ion complexes is required for their rational integration into light-driven reactions of chemical and biological interest. However, in contrast to mononuclear systems, the multidimensional dynamics of the PSS in solvated molecular arrays have not yet been elucidated due to the expected complications associated with the connectivity between the metal centers and the strong interactions with the surroundings. In this work, the PSS in a solvated triiron(II) metallogrid complex is characterized using transient optical absorption and X-ray emission spectroscopies on the femtosecond time scale. The complementary measurements reveal the photoinduced creation of energy-rich (hot) and long-lived quintet states, whose dynamics differ critically from their mononuclear congeners. This finding opens major prospects for developing novel schemes in solution-phase spin chemistry that are driven by the dynamic PSS process in compact oligometallic arrays.

Objectives: This study examined the potential moderating role of trait mindfulness on the association between perceived sexual racism and psychological symptoms among a community-based sample of ethnic/racial minority young men who have sex with men (MSM) residing in greater Los Angeles., Methods: From a cross-sectional sample of 448 participants, aged 16-24 years, survey data were analyzed to examine rates of perceived sexual racism, mindfulness, psychological symptoms, and moderation by mindfulness through various analyses, including analysis of variance and logistic regression., Results: Results indicated that Latino young MSM reported the lowest scores of sexual racism, and sexual racism was associated with higher odds of psychological symptoms, suicidal ideation with a plan in the past year, and self-injury in the past 3 months. The protective potential of mindfulness was suggested by its main effects on psychological symptoms; however, it only buffered the effects of sexual racism on suicidal ideation with a plan and self-injury, with marginal buffering effects on depression., Conclusions: Findings underscore the potential utility of assessing sexual racism among young MSM of color, as well as the potential benefit of mindfulness approaches to buffer the effects of sexual racism on symptoms of depression. Interpretation of these findings is briefly discussed., Competing Interests: Conflict of Interest The authors declare that they have no conflicts of interest.

This study tested the hypothesis that people using pre-exposure prophylaxis (PrEP) would be more likely to report condomless anal sex than those not taking PrEP. Data were from an ongoing study conducted with a cohort of Black and Latino young men who have sex with men (YMSM) recruited in Los Angeles (CA, USA). Of the 399 YMSM in the sample, 14% were currently using PrEP. Using three different measures of condom use, across two different recall periods all except one test result supported an inverse relationship between PrEP and condom use for anal sex. Tests of a risk index provided further significant findings supporting this hypothesis.

The European X-ray Free-Electron Laser (EuXFEL) delivers extremely intense (>10 12  photons pulse -1 and up to 27000 pulses s -1 ), ultrashort (<100 fs) and transversely coherent X-ray radiation, at a repetition rate of up to 4.5 MHz. Its unique X-ray beam parameters enable novel and groundbreaking experiments in ultrafast photochemistry and material sciences at the Femtosecond X-ray Experiments (FXE) scientific instrument. This paper provides an overview of the currently implemented experimental baseline instrumentation and its performance during the commissioning phase, and a preview of planned improvements. FXE's versatile instrumentation combines the simultaneous application of forward X-ray scattering and X-ray spectroscopy techniques with femtosecond time resolution. These methods will eventually permit exploitation of wide-angle X-ray scattering studies and X-ray emission spectroscopy, along with X-ray absorption spectroscopy, including resonant inelastic X-ray scattering and X-ray Raman scattering. A suite of ultrafast optical lasers throughout the UV-visible and near-IR ranges (extending up to mid-IR in the near future) with pulse length down to 15 fs, synchronized to the X-ray source, serve to initiate dynamic changes in the sample. Time-delayed hard X-ray pulses in the 5-20 keV range are used to probe the ensuing dynamic processes using the suite of X-ray probe tools. FXE is equipped with a primary monochromator, a primary and secondary single-shot spectrometer, and a timing tool to correct the residual timing jitter between laser and X-ray pulses., (open access.)

Sexual minority individuals experience barriers to receiving equitable health care. Research also indicates that young men who have sex with men (YMSM), particularly young men of color, have limited engagement in the HIV care continuum and there are significant disparities across the continuum. This study aims to uncover how providers can engage YMSM of color in all forms of care, including primary care and HIV prevention through an HIV prevention continuum. This qualitative study reports data from the Healthy Young Men's Cohort Study; a total of 49 YMSM participated in the eight focus groups. This study provides a description of YMSM's overall health concerns, experiences with health care, and under what circumstances YMSM seek care. We then present a model describing the salient characteristics of a HIV prevention continuum for YMSM of color and provide clear areas for education, intervention, and policy change to support better overall health for YMSM of color.

Background: We have limited information on families' experiences during transition and after discharge from the neonatal intensive care unit., Methods: Open-ended semi-structured interviews were conducted with English or Spanish- speaking families enrolled in Medicaid in an urban high-risk infant follow up clinic at a safety-net center, which serves preterm and high-risk term infants. We generated salient themes using inductive-deductive thematic analysis., Results: Twenty-one participants completed the study. The infant's median (IQR) birth weight was 1750 (1305, 2641) grams; 71% were Hispanic and 10% were Black non-Hispanic; 62% reported living in a neighborhood with 3-4th quartile economic hardship. All were classified as having chronic disease per the Pediatric Medical Complexity Algorithm and 67% had medical complexity. A conceptual model was constructed and the analysis revealed major themes describing families' challenges and ideas to support transition centered on the parent-child role and parent self-efficacy. The challenges were: (1) comparison to normal babies, (2) caregiver mental health, (3) need for information. Ideas to support transition included, (1) support systems, (2) interventions using mobile health technology (3) improved communication to the primary care provider and (4) information regarding financial assistance programs. Specific subthemes differed in frequency counts between infants with and without medical complexity., Conclusions: Families often compare their preterm or high-risk infant to their peers and mothers feel great anxiety and stress. However, families often found hope and resilience in peer support and cited that in addition to information needs, interventions using mobile health technology and transition and financial systems could better support families after discharge.

Background: No group is at greater risk for acquiring HIV than young men who have sex with men (YMSM), particularly black or African American (AA) and Hispanic or Latino (L) YMSM living in inner cities, who account for the largest number of new HIV infections each year. Although pre-exposure prophylaxis (PrEP), postexposure prophylaxis (PEP), and treatment as prevention hold enormous promise for changing the course of the epidemic, AA/L-YMSM are the least likely population to be receiving primary health care and HIV prevention/care and are the least likely to be using PrEP and PEP., Objective: The overarching aim of the Healthy Young Men's (HYM) cohort study is to conduct longitudinal research with a cohort of AA/L-YMSM to prevent new HIV infections, reduce transmission, and reduce HIV/AIDS-related disparities by focusing on successful engagement in care. Findings from this research will be used to inform the development of new interventions designed to engage AA/L-YMSM in the HIV prevention and care continua., Methods: Longitudinal research (baseline and follow-up assessments every 6 months for a total of 8 waves of data collection) is ongoing with a new cohort of 450 high-risk AA/L-YMSM in Los Angeles. Participants were recruited using a venue-based and social media sampling design. In addition to self-report surveys, the study protocol includes the collection of urine to assess recent use of illicit drugs and the collection of blood and rectal/throat swabs to test for current sexually transmitted infection (STI)/HIV infection. An additional sample of blood/plasma (10 mL for 4 aliquots and 1 pellet) is also collected and stored in the HYM cohort study biorepository for future research. By design, we recruited 400 HIV-negative participants and 50 HIV-positive (HIV+) participants. This mixed-methods study design includes collection and triangulated analysis of quantitative, qualitative, and biological measures (ie, drug use, STI/HIV testing, and adherence to antiretroviral therapy among HIV+ participants) at baseline and every 6 months. The HYM cohort study will provide a platform from which new and emerging biomedical prevention strategies (eg, PrEP, rectal microbicides, and PEP) and other HIV prevention and care engagement interventions can be developed and evaluated with AA/L-YMSM., Results: To date, all participants in the HYM cohort study have been recruited and baseline assessment has been conducted., Conclusions: The findings from this research will be used to inform the development of new and/or adaptation of existing evidence-based HIV prevention interventions and interventions designed to engage this population in the HIV prevention and care continua., International Registered Report Identifier (irrid): DERR1-10.2196/10738., (©Michele D Kipke, Katrina Kubicek, Carolyn F Wong, Yolo Akili Robinson, Ifedayo C Akinyemi, William J Beyer, Wendy Hawkins, Cara E Rice, Eric Layland, Bethany C Bray, Marvin Belzer. Originally published in JMIR Research Protocols (http://www.researchprotocols.org), 24.01.2019.)

Background: Diabetes disproportionately affects the US Latino population, due to socioeconomic pressures, genetics, reduced access to care and cultural practices. While efforts to improve self-care through interventions incorporating family are highly rated by Latinos, family can be both supportive and obstructive. To develop effective interventions, this role needs clarification., Methods: We conducted group interviews in Spanish and English with 24 participants with diabetes from a mobile health diabetes self-care intervention. We imported transcripts into Dedoose, a qualitative computer analysis program and analyzed them with a modified grounded theory technique. Utilizing an iterative process, we reexamined transcripts with new codes derived in each round of analysis until saturation was reached. We employed techniques to improve trustworthiness (co-coding, member checking). Broad categorical themes arose from the initial codes and were developed into a conceptual model of barriers to and strategies for diabetes management., Results: Family and family responsibilities emerged as both a supportive and obstructive force for diabetes self-care. While the desire to care for family motivated patients, food at family gatherings and pressure from managing multiple family responsibilities contributed to poor diet choices. Yet, some patients believed their diabetes caused their immediate family to make healthier choices., Conclusions: Among these predominantly Latino patients, family and family responsibilities were key motivators as well as obstacles to self-care, particularly regarding nutrition. Finding the ideal design for social support mHealth-based interventions will require careful study and creation of culturally based programs to match the needs of specific populations, and may require educating family members to provide effective social support.

Research investigating intimate partner violence (IPV) among sexual minorities is limited. The research that does exist has found that rates of IPV are similar to or higher than the rates found for heterosexual women, the most commonly studied population in this area. This limited research has resulted in a dearth of prevention/intervention programs targeted for these populations. While some may argue that existing IPV programs can be used for these populations, this review presents an argument for more targeted work with sexual minority populations, using young men who have sex with men (YMSM) as an example. Drawing on the framework of intersectionality, this article argues that the intersectionality of age, sexual identity, and gender combines to create a spectrum of unique factors that require specific attention. This framework allows for the identification of known correlates for IPV as well as factors that may be unique to YMSM or other sexual minority populations. The article presents a conceptual model that suggests new areas of research as well as a foundation for the topics and issues that should be addressed in an intervention.

RNA polymerase II contains a long C-terminal domain (CTD) that regulates interactions at the site of transcription. The CTD architecture remains poorly understood due to its low sequence complexity, dynamic phosphorylation patterns, and structural variability. We used integrative structural biology to visualize the architecture of the CTD in complex with Rtt103, a 3'-end RNA-processing and transcription termination factor. Rtt103 forms homodimers via its long coiled-coil domain and associates densely on the repetitive sequence of the phosphorylated CTD via its N-terminal CTD-interacting domain. The CTD-Rtt103 association opens the compact random coil structure of the CTD, leading to a beads-on-a-string topology in which the long rod-shaped Rtt103 dimers define the topological and mobility restraints of the entire assembly. These findings underpin the importance of the structural plasticity of the CTD, which is templated by a particular set of CTD-binding proteins., Competing Interests: The authors declare no conflict of interest., (Copyright © 2017 the Author(s). Published by PNAS.)

Phosphorylation patterns of the C-terminal domain (CTD) of largest subunit of RNA polymerase II (called the CTD code) orchestrate the recruitment of RNA processing and transcription factors. Recent studies showed that not only serines and tyrosines but also threonines of the CTD can be phosphorylated with a number of functional consequences, including the interaction with yeast transcription termination factor, Rtt103p. Here, we report the solution structure of the Rtt103p CTD-interacting domain (CID) bound to Thr4 phosphorylated CTD, a poorly understood letter of the CTD code. The structure reveals a direct recognition of the phospho-Thr4 mark by Rtt103p CID and extensive interactions involving residues from three repeats of the CTD heptad. Intriguingly, Rtt103p's CID binds equally well Thr4 and Ser2 phosphorylated CTD A doubly phosphorylated CTD at Ser2 and Thr4 diminishes its binding affinity due to electrostatic repulsion. Our structural data suggest that the recruitment of a CID-containing CTD-binding factor may be coded by more than one letter of the CTD code., (© 2017 The Authors. Published under the terms of the CC BY 4.0 license.)

Problem: A goal of the Southern California Clinical and Translational Science Institute (SC-CTSI) at the University of Southern California and Children's Hospital Los Angeles is to train early-stage clinical and translational scientists (CTSs) to conduct research that improves the health of diverse communities. This goal aligns well with the Institute of Medicine's recommendations emphasizing community engagement in biomedical research that facilitates research translation. The Community Mentorship Program (CMP), created to complement community-engaged research didactics, matches CTSs with community mentors who help them identify and complete community-engaged experiences that inform their research., Approach: The CMP was piloted in 2013-2015 by the SC-CTSI Workforce Development and Community Engagement cores. The CMP team matched three CTSs (assistant professors pursuing mentored career development awards) with mentors at community-based organizations (CBOs) aligned with their research interests. Each mentor-mentee pair signed a memorandum of understanding. The CMP team checked in regularly, monitoring progress and addressing challenges in CTSs' completion of their community-engaged experience., Outcomes: Each pair completed at least one community-engaged activity informing the CTS's research. In exit interviews, the CTSs and CBO mentors expressed satisfaction with the program and stated that they would continue to work together. The CTSs reported that the program provided opportunities to develop networks outside academia, build trust within the community, and receive feedback and learn from individuals in communities affected by their research., Next Steps: The CMP will be expanded to include all eligible early-career CTSs and promoted for use in similar settings outside the SC-CTSI.

Background and Importance: Challenges in healthcare policy and practice have stimulated interest in dissemination and implementation science. The Institute of Medicine Committee on the Clinical Translational Science Award (CTSA) program recommended expanding the CTSA program's investment and activity in this domain. Guidance is needed to facilitate successful growth of DII science infrastructure, activity and impacts., Objectives: Several CTSAs in Southern California collaborated to identify and respond to local challenges and opportunities to expand dissemination, implementation and improvement research by strengthening capacity and relationships between DII researchers and community, health system, and population health partners., Main Outcomes: Planning and outreach by the Southern California CTSAs increased awareness and interest in DII research and generated recommendations for growth. Recommendations include: increasing strong partnerships with healthcare and population health systems to guide policy research agendas and collaborative DII science; promoting multi-sector partnerships that involve researchers and delivery systems throughout DII processes; bringing together multiple disciplines; and addressing national and international barriers as well as opportunities in DII science., Implications: CTSAs through regional collaboration can increase their contributions to improved community health via skill-building, partnership development and enhanced outreach to local healthcare and public health agencies and delivery systems., (© 2015 Wiley Periodicals, Inc.)

Objective: To describe weight, body mass index (BMI), blood pressure (BP), lipids, and hormone levels in transgender women and men presenting for initiation of cross-sex hormone therapy at a community clinic in the United States., Methods: Twenty-three transgender women (persons assigned male at birth who identify as female and want to use estrogen to develop female secondary sex characteristics) and 34 transgender men (persons assigned female at birth who identify as male and want to use testosterone to develop male secondary sex characteristics) presenting for initiation of hormone therapy at a community health center were enrolled. Body mass index, BP, lipids, and sex hormone levels were measured at baseline and 6 months. Persistence of menses at 6 months in transgender men was recorded., Results: Sixteen transgender women and 31 transgender men completed the study. Baseline and 6-month median BPs and lipid values were within a normal clinical range. Median systolic BP in transgender women dropped from baseline 130.5 mmHg (interquartile range 11.5) to 120.5 mmHg (interquartile range 15.5) at 6 months (P=.006). Testosterone levels remained elevated in 33% and estradiol (E2) levels were supratherapeutic in 19% of transgender women at 6 months. Median BMI for transgender men was 29.1 kg/m (interquartile range 11.2) at baseline and 30.0 kg/m (interquartile range 11.4) at 6 months (P=.024). Six-month total testosterone levels were subtherapeutic in 32% and E2 levels remained elevated in 71% of transgender men., Conclusion: In transgender women, estrogen therapy, with or without antiandrogen therapy, was associated with lower BP. In transgender men, testosterone therapy was associated with increased BMI. The study had insufficient power to detect other associations. Monitoring of hormone levels to guide therapy appears to be useful., Level of Evidence: III.

In the third decade of the HIV/AIDS epidemic in the United States, the prevalence rates of new HIV infections among young men who have sex with men (YMSM) continue to increase. As new and emerging HIV prevention methods are developed, it is important to understand the perceptions of this vulnerable population-as they may be an ideal target for these intervention methods. This pilot study provides an overview of YMSM of color's awareness and perceptions of pre-exposure prophylaxis (PrEP) and rectal microbicides (RM). A total of 6 focus groups were convened with 53 YMSM (23 Latino/Hispanic and 30 Black/African American). Findings indicate a lack of knowledge of biomedical interventions and high perceived acceptability. Concerns regarding PrEP included potential side effects, potential for misinterpretation of its use and cost. RMs were perceived to be more acceptable than PrEP, but the limited knowledge about their potential was emphasized by YMSM. Results are discussed in relation to the need for providers to continue to provide general health education about safe sexual practices. As PrEP and other biomedical interventions are introduced into community settings, caution should be taken with regards to determining the appropriate target user and sufficient education.

The structure of bulk liquid water was recently probed by x-ray scattering below the temperature limit of homogeneous nucleation (TH) of ∼232 K [J. A. Sellberg et al., Nature 510, 381-384 (2014)]. Here, we utilize a similar approach to study the structure of bulk liquid water below TH using oxygen K-edge x-ray emission spectroscopy (XES). Based on previous XES experiments [T. Tokushima et al., Chem. Phys. Lett. 460, 387-400 (2008)] at higher temperatures, we expected the ratio of the 1b1' and 1b1″ peaks associated with the lone-pair orbital in water to change strongly upon deep supercooling as the coordination of the hydrogen (H-) bonds becomes tetrahedral. In contrast, we observed only minor changes in the lone-pair spectral region, challenging an interpretation in terms of two interconverting species. A number of alternative hypotheses to explain the results are put forward and discussed. Although the spectra can be explained by various contributions from these hypotheses, we here emphasize the interpretation that the line shape of each component changes dramatically when approaching lower temperatures, where, in particular, the peak assigned to the proposed disordered component would become more symmetrical as vibrational interference becomes more important.

Young men who have sex with men (YMSM) continue to experience higher rates of HIV infection than other populations. Recently, there have been recommendations to consider HIV prevention at the dyadic or couple level. Using a dyadic approach to HIV prevention would also address an unaddressed concern related to intimate partner violence (IPV) among YMSM. Although research on IPV among YMSM is still in its infancy, great strides have been made in the past 10 years to describe the prevalence and related correlates of IPV within older adult same-sex relationships. These studies have found rates of IPV among MSM to be similar to rates among heterosexual women, and to be on the rise. The present study is designed to provide insight into how power is conceptualized within YMSM relationships and the role it may play in relationship challenges. This study draws from qualitative data collected from 11 focus groups with 86 YMSM and 26 individual semi-structured interviews to understand relationship challenges and the experiences of YMSM involved in partner violence. YMSM described relationship power as stemming from numerous sources including sexual positioning, gender roles, education, income, prior relationship experiences, and internalized homophobia. The findings have a number of implications for service providers and program design. Interventionists and other researchers need to consider power dynamics and other contextual elements of IPV before effective interventions can be developed for YMSM and other sexual minority populations., (© The Author(s) 2014.)

Filipino Americans are the second largest immigrant population and second largest Asian ethnic group in the U.S. Disparities in youth behavioral health problems and the receipt of mental health services among Filipino youth have been documented previously. However, few studies have elicited perspectives from community stakeholders regarding how to prevent mental health disparities among Filipino youth. The purpose of the current study is to identify intervention strategies for implementing mental health prevention programs among Filipino youth. We conducted semi-structured interviews (n=33) with adolescents, caregivers, advocates, and providers and focus groups (n=18) with adolescents and caregivers. Interviews were audio taped and transcribed verbatim. Transcripts were analyzed using a methodology of "coding consensus, co-occurrence, and comparison" and was rooted in grounded theory. Four recommendations were identified when developing mental health prevention strategies among Filipino populations: address the intergenerational gap between Filipino parents and children, provide evidence-based parenting programs, collaborate with churches in order to overcome stigma associated with mental health, and address mental health needs of parents. Findings highlight the implementation of evidence-based preventive parenting programs in faith settings as a community-identified and culturally appropriate strategy to prevent Filipino youth behavioral health disparities.

We report on oxygen K-edge soft x-ray emission spectroscopy from a liquid water jet at the Linac Coherent Light Source. We observe significant changes in the spectral content when tuning over a wide range of incident x-ray fluences. In addition the total emission yield decreases at high fluences. These modifications result from reabsorption of x-ray emission by valence-excited molecules generated by the Auger cascade. Our observations have major implications for future x-ray emission studies at intense x-ray sources. We highlight the importance of the x-ray pulse length with respect to the core-hole lifetime.

The Nrd1-Nab3-Sen1 (NNS) complex is essential for controlling pervasive transcription and generating sn/snoRNAs in S. cerevisiae. The NNS complex terminates transcription of noncoding RNA genes and promotes exosome-dependent processing/degradation of the released transcripts. The Trf4-Air2-Mtr4 (TRAMP) complex polyadenylates NNS target RNAs and favors their degradation. NNS-dependent termination and degradation are coupled, but the mechanism underlying this coupling remains enigmatic. Here we provide structural and functional evidence demonstrating that the same domain of Nrd1p interacts with RNA polymerase II and Trf4p in a mutually exclusive manner, thus defining two alternative forms of the NNS complex, one involved in termination and the other in degradation. We show that the Nrd1-Trf4 interaction is required for optimal exosome activity in vivo and for the stimulation of polyadenylation of NNS targets by TRAMP in vitro. We propose that transcription termination and RNA degradation are coordinated by switching between two alternative partners of the NNS complex., (Copyright © 2014 Elsevier Inc. All rights reserved.)

In the current work, X-ray emission spectra of aqueous solutions of different inorganic salts within the Hofmeister series are presented. The results reflect the direct interaction of the ions with the water molecules and therefore, reveal general properties of the salt-water interactions. Within the experimental precision a significant effect of the ions on the water structure has been observed but no ordering according to the structure maker/structure breaker concept could be mirrored in the results indicating that the Hofmeister effect-if existent-may be caused by more complex interactions.

In Saccharomyces cerevisiae, the Nrd1-dependent termination and processing pathways play an important role in surveillance and processing of non-coding ribonucleic acids (RNAs). The termination and subsequent processing is dependent on the Nrd1 complex consisting of two RNA-binding proteins Nrd1 and Nab3 and Sen1 helicase. It is established that Nrd1 and Nab3 cooperatively recognize specific termination elements within nascent RNA, GUA[A/G] and UCUU[G], respectively. Interestingly, some transcripts do not require GUA[A/G] motif for transcription termination in vivo and binding in vitro, suggesting the existence of alternative Nrd1-binding motifs. Here we studied the structure and RNA-binding properties of Nrd1 using nuclear magnetic resonance (NMR), fluorescence anisotropy and phenotypic analyses in vivo. We determined the solution structure of a two-domain RNA-binding fragment of Nrd1, formed by an RNA-recognition motif and helix-loop bundle. NMR and fluorescence data show that not only GUA[A/G] but also several other G-rich and AU-rich motifs are able to bind Nrd1 with affinity in a low micromolar range. The broad substrate specificity is achieved by adaptable interaction surfaces of the RNA-recognition motif and helix-loop bundle domains that sandwich the RNA substrates. Our findings have implication for the role of Nrd1 in termination and processing of many non-coding RNAs arising from bidirectional pervasive transcription., (© The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Objectives: We investigated the roles of House membership and the influence of social and sexual network members on the sexual risk behavior of men in the Los Angeles House and Ball community., Methods: From February 2009 to January 2010, male participants (n = 233) completed interviewer-assisted surveys during a House meeting or Ball event. We used logistic regression to model the effects of sexual network size, influence of sexual network members, House membership status, and their interactions on high-risk sex., Results: Significant predictors of high-risk sex included number of sexual partners in the nominated social network, multiethnicity, and previous diagnosis of sexually transmitted infection. House membership was protective against high-risk sex. Additionally, a 3-way interaction emerged between number of sexual partners in the network, influence, and network members' House membership., Conclusions: Future research should assess network members' attitudes and behavior in detail to provide a greater understanding of the dynamics of social influence and to identify additional avenues for intervention.