Micronutrient dose response (MiNDR) study among women of reproductive age and pregnant women in rural Bangladesh: study protocol for double-blind, randomised, controlled trials.

Introduction: Optimising the micronutrient status of women before and during reproduction confers benefits to them and their offspring. Antenatal multiple micronutrient supplements (MMS), given as a daily tablet with nutrients at ~1 recommended dietary allowance (RDA) or adequate intake (AI) reduces adverse birth outcomes. However, at this dosage, MMS may not fully address micronutrient deficiencies in settings with chronically inadequate diets and infection.

Targeting strategies for balanced energy and protein (BEP) supplementation in pregnancy: study protocol for the TARGET-BEP cluster-randomized controlled trial in rural Bangladesh.

Background: The World Health Organization (WHO) recommends balanced energy and protein (BEP) supplementation be provided to all pregnant women living in undernourished populations, usually defined as having a prevalence > 20% of underweight women, to reduce the risk of stillbirths and small-for-gestational-age neonates. Few geographies meet this threshold, however, and a large proportion of undernourished women and those with inadequate gestational weight gain could miss benefiting from BEP. This study compares the effectiveness of individual targeting approaches for supplementation with micronutrient-fortified BEP vs.

The Pregnancy, Arsenic, and Immune Response (PAIR) Study in rural northern Bangladesh.

Background: Arsenic exposure and micronutrient deficiencies may alter immune reactivity to influenza vaccination in pregnant women, transplacental transfer of maternal antibodies to the foetus, and maternal and infant acute morbidity.

Objectives: The Pregnancy, Arsenic, and Immune Response (PAIR) Study was designed to assess whether arsenic exposure and micronutrient deficiencies alter maternal and newborn immunity and acute morbidity following maternal seasonal influenza vaccination during pregnancy.

Population: The PAIR Study recruited pregnant women across a large rural study area in Gaibandha District, northern Bangladesh, 2018-2019.

Comparison of the Role of Protein Dynamics in Catalysis by Dihydrofolate Reductase from and .

Dihydrofolate reductase (DHFR) is a well-studied, clinically relevant enzyme known for being highly dynamic over the course of its catalytic cycle. However, the role dynamic motions play in the explicit hydride transfer from the nicotinamide cofactor to the dihydrofolate substrate remains unclear because reaction initiation and direct spectroscopic examination on the appropriate time scale for such femtosecond to picosecond motions is challenging. Here, we employ pre-steady-state kinetics to observe the hydride transfer as directly as possible in two different species of DHFR: and .

Time-Resolved Infrared Spectroscopy Reveals the pH-Independence of the First Electron Transfer Step in the [FeFe] Hydrogenase Catalytic Cycle.

[FeFe] hydrogenases are highly active catalysts for hydrogen conversion. Their active site has two components: a [4Fe-4S] electron relay covalently attached to the H binding site and a diiron cluster ligated by CO, CN, and 2-azapropane-1,3-dithiolate (ADT) ligands. Reduction of the [4Fe-4S] site was proposed to be coupled with protonation of one of its cysteine ligands.

Efficient, Light-Driven Reduction of CO to CO by a Carbon Monoxide Dehydrogenase-CdSe/CdS Nanorod Photosystem.

The solar conversion of CO to low carbon fuels has been heralded as a potential solution to combat the rise in greenhouse gas emissions. Here we report the first light-driven activation of [NiFe] CODH II from for the reduction of CO to CO. To accomplish this, a hybrid photosystem composed of CODH II and CdSe/CdS dot-in-rod nanocrystals was developed.

Massively Parallelized Molecular Force Manipulation with On-Demand Thermal and Optical Control.

In single-molecule force spectroscopy (SMFS), a tethered molecule is stretched using a specialized instrument to study how macromolecules extend under force. One problem in SMFS is the serial and slow nature of the measurements, performed one molecule at a time. To address this long-standing challenge, we report on the origami polymer force clamp (OPFC) which enables parallelized manipulation of the mechanical forces experienced by molecules without the need for dedicated SMFS instruments or surface tethering.

Stability of HA2 Prefusion Structure and pH-Induced Conformational Changes in the HA2 Domain of H3N2 Hemagglutinin.

Influenza hemagglutinin is the fusion protein that mediates fusion of the viral and host membranes through a large conformational change upon acidification in the developing endosome. The "spring-loaded" model has long been used to describe the mechanism of hemagglutinin and other type 1 viral glycoproteins. This model postulates a metastable conformation of the HA2 subunit, caged from adopting a lower-free energy conformation by the HA1 subunit.

Metal-ligand cooperativity in the soluble hydrogenase-1 from .

Metal-ligand cooperativity is an essential feature of bioinorganic catalysis. The design principles of such cooperativity in metalloenzymes are underexplored, but are critical to understand for developing efficient catalysts designed with earth abundant metals for small molecule activation. The simple substrate requirements of reversible proton reduction by the [NiFe]-hydrogenases make them a model bioinorganic system.

Acceleration of catalysis in dihydrofolate reductase by transient, site-specific photothermal excitation.

We have studied the role of protein dynamics in chemical catalysis in the enzyme dihydrofolate reductase (DHFR), using a pump-probe method that employs pulsed-laser photothermal heating of a gold nanoparticle (AuNP) to directly excite a local region of the protein structure and transient absorbance to probe the effect on enzyme activity. Enzyme activity is accelerated by pulsed-laser excitation when the AuNP is attached close to a network of coupled motions in DHFR (on the FG loop, containing residues 116-132, or on a nearby alpha helix). No rate acceleration is observed when the AuNP is attached away from the network (distal mutant and His-tagged mutant) with pulsed excitation, or for any attachment site with continuous wave excitation.

Shape-Shifting Peptide Nanomaterials: Surface Asymmetry Enables pH-Dependent Formation and Interconversion of Collagen Tubes and Sheets.

The fabrication of dynamic, transformable biomaterials that respond to environmental cues represents a significant step forward in the development of synthetic materials that rival their highly functional, natural counterparts. Here, we describe the design and synthesis of crystalline supramolecular architectures from charge-complementary heteromeric pairs of collagen-mimetic peptides (CMPs). Under appropriate conditions, CMP pairs spontaneously assemble into either 1D ultraporous (pore diameter >100 nm) tubes or 2D bilayer nanosheets due to the structural asymmetry that arises from heteromeric self-association.

The Laser-Induced Potential Jump: A Method for Rapid Electron Injection into Oxidoreductase Enzymes.

Oxidoreductase enzymes often perform technologically useful chemical transformations using abundant metal cofactors with high efficiency under ambient conditions. The understanding of the catalytic mechanism of these enzymes is, however, highly dependent on the availability of well-characterized and optimized time-resolved analytical techniques. We have developed an approach for rapidly injecting electrons into a catalytic system using a photoactivated nanomaterial in combination with a range of redox mediators to produce a potential jump in solution, which then initiates turnover via electron transfer (ET) to the catalyst.

Site-Specific Tryptophan Labels Reveal Local Microsecond-Millisecond Motions of Dihydrofolate Reductase.

Many enzymes are known to change conformations during their catalytic cycle, but the role of these protein motions is not well understood. dihydrofolate reductase (DHFR) is a small, flexible enzyme that is often used as a model system for understanding enzyme dynamics. Recently, native tryptophan fluorescence was used as a probe to study micro- to millisecond dynamics of DHFR.

Surface-Ligand "Liquid" to "Crystalline" Phase Transition Modulates the Solar H Production Quantum Efficiency of CdS Nanorod/Mediator/Hydrogenase Assemblies.

This study reports how the length of capping ligands on a nanocrystal surface affects its interfacial electron transfer (ET) with surrounding molecular electron acceptors, and consequently, impact the H production of a biotic-abiotic hybrid artificial photosynthetic system. Specifically, we study how the H production efficiency of a hybrid system, combining CdS nanorods (NRs), [NiFe] hydrogenase, and redox mediators (propyl-bridged 2,2'-bipyridinium, PDQ), depends on the alkyl chain length of mercaptocarboxylate ligands on the NR surface. We observe a minor decrease of the quantum yield for H production from 54 ± 6 to 43 ± 2% when varying the number of methylene units in the ligands from 2 to 7.

Investigating the Kinetic Competency of HydA1 [FeFe] Hydrogenase Intermediate States via Time-Resolved Infrared Spectroscopy.

Hydrogenases are metalloenzymes that catalyze the reversible oxidation of H. The [FeFe] hydrogenases are generally biased toward proton reduction and have high activities. Several different catalytic mechanisms have been proposed for the [FeFe] enzymes based on the identification of intermediate states in equilibrium and steady state experiments.

Kinetics of Histidine-Tagged Protein Association to Nickel-Decorated Liposome Surfaces.

Nickel-chelating lipids offer a convenient platform for reversible immobilization of histidine-tagged proteins to liposome surfaces. This interaction recently found utility as a model system for studying membrane remodeling triggered by protein crowding. Despite its wide array of utility, the molecular details of transient protein association to the lipid surfaces decorated with such chelator lipids remains poorly understood.

Active-Site Glu165 Activation in Triosephosphate Isomerase and Its Deprotonation Kinetics.

Triosephosphate isomerase (TIM) catalyzes the interconversion between dihydroxyacetone phosphate (DHAP) and d-glyceraldehyde 3-phosphate (GAP) via an enediol(ate) intermediate. The active-site residue Glu165 serves as the catalytic base during catalysis. It abstracts a proton from C1 carbon of DHAP to form the reaction intermediate and donates a proton to C2 carbon of the intermediate to form product GAP.

Optimizing electron transfer from CdSe QDs to hydrogenase for photocatalytic H production.

A series of viologen related redox mediators of varying reduction potential has been characterized and their utility as electron shuttles between CdSe quantum dots and hydrogenase enzyme has been demonstrated. Tuning the mediator LUMO energy optimizes the performance of this hybrid photocatalytic system by balancing electron transfer rates of the shuttle.

A quantitative connection of experimental and simulated folding landscapes by vibrational spectroscopy.

For small molecule reaction kinetics, computed reaction coordinates often mimic experimentally measured observables quite accurately. Although nowadays simulated and measured biomolecule kinetics can be compared on the same time scale, a gap between computed and experimental observables remains. Here we directly compared temperature-jump experiments and molecular dynamics simulations of protein folding dynamics using the same observable: the time-dependent infrared spectrum.

Localized Nanoscale Heating Leads to Ultrafast Hydrogel Volume-Phase Transition.

The rate of the volume-phase transition for stimuli-responsive hydrogel particles ranging in size from millimeters to nanometers is limited by the rate of water transport, which is proportional to the surface area of the particle. Here, we hypothesized that the rate of volume-phase transition could be accelerated if the stimulus is geometrically controlled from the inside out, thus facilitating outward water ejection. To test this concept, we applied transient absorption spectroscopy, laser temperature-jump spectroscopy, and finite-element analysis modeling to characterize the dynamics of the volume-phase transition of hydrogel particles with a gold nanorod core.

Small molecule cores demonstrate non-competitive inhibition of lactate dehydrogenase.

Lactate dehydrogenase (LDH) has recently garnered attention as an attractive target for cancer therapies, owing to the enzyme's critical role in cellular metabolism. Current inhibition strategies, employing substrate or cofactor analogues, are insufficiently specific for use as pharmaceutical agents. The possibility of allosteric inhibition of LDH was postulated on the basis of theoretical docking studies of a small molecule inhibitor to LDH.

Heterogeneity in the Folding of Villin Headpiece Subdomain HP36.

Small single domain proteins that fold on the microsecond time scale have been the subject of intense interest as models for probing the complexity of folding energy landscapes. The villin headpiece subdomain (HP36) has been extensively studied because of its simple three helix structure, ultrafast folding lifetime of a few microseconds, and stable native fold. We have previously shown that folding as measured by a single C═O isotopic label on residue A57 in helix 2 occurs at a different rate than that measured by global probes of folding, indicating noncooperative complexity in the folding of HP36.