Specific Hydrogen Bonds Research Articles

Vitamin C Mitigating and Rescuing from Synergistic Toxicity: Sodium Fluoride, Silicofluorides, Aluminum Salts, Electromagnetic Pollution, and SARS-CoV-2

A supramolecular paradigm for mitigation and rescue from SARS-COV2 infection is proposed. Similarities between the Sanarelli-Shwartzman phenomenon and biological responses to viral pathogens are considered. Non-enzymatic group transfer catalysis (NGTC) by L-ascorbic acid, the L-ascorbic acid free radical and the 2-O-phosphate substituted L-ascorbic acid derivative are proposed under the ascorbolysis hypothesis to provide a supramolecular basis for mitigating the synergistic toxicity and catalytic mimicry by the environmental toxicants, sodium fluoride, aluminum salts, and silicofluorides in public water supplies. Ascorbolysis is the term we adopt to describe a redox active, hyperconjugated, vinylogous variant of acidolysis. The objective of this paper is to provide a plausible supramolecular basis for mitigation and rescue from well-known environmental toxicity represented by the presence of sodium fluoride, aluminum salts, and silicofluoride species in public water supplies. An overview of the conceptual basis for NGTC by vitamin C during inflammatory states is provided. Controversies concerning the initial oxidation steps and pH-dependent speciation of L-ascorbic acid are addressed. Non-skeletal fluorosis is a serious systemic malady which we propose arises from disruption of hydrogen bond networks and hydrogen bond cooperativity resulting from the marked electronegativity and hydrogen bond accepting ability of fluoride atoms found in NaF and AlFx species. AlFx species have been previously shown to arise in situ spontaneously from NaF, aluminum salts, and silicofluorides often found in toothpastes and “fluoridated” drinking water. AlFx species are thought to act as isosteric mimics of biophosphates during group transfers of phosphoryl moieties. We propose that catalytic mimicry by AlFx species inhibits postulated non-enzymatic kinase-like and RNA polymerase-like function of the AA-2P derivative during inflammatory states. We describe how NGTC by L-ascorbic acid is likely to be disrupted by AlFx and sodium fluoride of a specific H3-O2 intramolecular hydrogen bond in L-ascorbic acid, the L-ascorbic acid free radical, and their 2-O-substituted derivatives, which are necessary for NGTC in the moderately acidic, mildly oxidative, relatively hydrophobic microenvironment which typify inflammatory states. Suggestions are made to achieve less variation in results of large randomized clinical trials (RCTs) seeking to validate use of high-dose intravenous vitamin C in critical care and cancer settings.

Combination of multiple computational methods revealing specific sub-sectional recognition and hydrogen-bond dependent transportation of CKII peptide fragment in O-GlcNAc transferase

O-linked β-N-acetyl-D-glucosamine (O-GlcNAc) transferase (OGT) is an essential enzyme in many cellular physiological catalytic reactions that regulates protein O-GlcNAcylation. Aberrant O-GlcNAcylation is related to insulin resistance, diabetic complications, cancer and neurodegenerative diseases. Understanding the peptide delivery in OGT is significant in comprehending enzymatic catalytic process, target-protein recognition and pathogenic mechanism. Herein extensive molecular dynamics (MD) simulations combined with various techniques are utilized to study the recognizing and binding mechanism of peptide fragment extracted from casein kinase II by OGT from atomic level. The residues of His496, His558, Thr633, Lys634, and Pro897 are demonstrated to play a dominant role in the peptide stabilization via hydrogen bonds and σ-π interaction, whose van der Waals and non-polar solvent effects provide the main driving force. In addition, two channels are identified. The delivery mode, mechanism together with thermodynamic and dynamic characterizations for the most favorable channel are determined. The peptide is more inclined to be recognized by OGT through the cavity comprised of residues 799–812, 893–899, and 865–871, and Tyr13-terminal is prior recognized to Met26-terminal. The transportation process is accompanied with conformation changes between the “spread” and “V” shapes. The whole process is strong exothermic that is highly dependent on the variation of hydrogen bond interactions between peptide and OGT as well as the performance of different subsections of peptide. Besides that, multiple computational methods combinations may contribute meaningfully to calculation of similar bio-systems with long and flexible substrate.

A comprehensive mechanism for 5-carboxylcytosine-induced transcriptional pausing revealed by Markov state models

RNA polymerase II (Pol II) surveils the genome, pausing as it encounters DNA lesions and base modifications and initiating signals for DNA repair among other important regulatory events. Recent work suggests that Pol II pauses at 5-carboxycytosine (5caC), an epigenetic modification of cytosine, because of a specific hydrogen bond between the carboxyl group of 5caC and a specific residue in fork loop 3 of Pol II. This hydrogen bond compromises productive NTP binding and slows down elongation. Apart from this specific interaction, the carboxyl group of 5caC can potentially interact with numerous charged residues in the cleft of Pol II. However, it is not clear how other interactions between Pol II and 5caC contribute to pausing. In this study, we use Markov state models (a type of kinetic network models) built from extensive molecular dynamics simulations to comprehensively study the impact of 5caC on Pol II translocation. We describe two translocation intermediates with specific interactions that prevent the template base from loading into the Pol II active site. In addition to the previously observed state with 5caC constrained by fork loop 3, we discovered a new intermediate state with a hydrogen bond between 5caC and fork loop 2. Surprisingly, we find that 5caC may curb translocation by suppressing kinking of the helix bordering the active site (the bridge helix) because its high flexibility is critical to translocation. Our work provides new insights into how epigenetic modifications of genomic DNA can modulate Pol II translocation, inducing pauses in transcription.

Unusual Spherulitic Morphology of Poly(propylene fumarate)

Spherulites are the most common crystalline morphology and thus the visual expression of crystal structures for polymers. The diversified patterns have provided intuitive morphology probes for various crystallization behaviors, while the correlations between them are still needed to be enriched. In this work, the complicated spherulitic morphology of poly(propylene fumarate) (PPF), which is sensitive to crystallization temperature, is investigated. PPF melt, respectively, crystallizes into rough spherulites, regularly banded spherulites, and spherulites containing both two kinds of morphology at low, high, and mediate temperatures. By systematically assaying, it is clear that the growth axis along the radial direction changes from a-axis to b-axis as the crystallization temperature increases, which leads to the formation of unique crystallization-temperature-dependent spherulites. Based on detailed characterization of Fourier transform infrared spectroscopy, the packing state of the specific hydrogen bonds of “C=C-H⋯O=C-C=C” in PPF crystal lattices is determined, and furthermore, the mechanism for temperature-dependent selection of growth axes for PPF spherulites in melt is reasonably speculated.

A Not Obvious Correlation Between the Structure of Green Fluorescent Protein Chromophore Pocket and Hydrogen Bond Dynamics: A Choreography From ab initio Molecular Dynamics.

The Green Fluorescent Protein (GFP) is a widely studied chemical system both for its large amount of applications and the complexity of the excited state proton transfer responsible of the change in the protonation state of the chromophore. A detailed investigation on the structure of the chromophore environment and the influence of chromophore form (either neutral or anionic) on it is of crucial importance to understand how these factors could potentially influence the protein function. In this study, we perform a detailed computational investigation based on the analysis of ab-initio molecular dynamics simulations, to disentangle the main structural quantities determining the fine balance in the chromophore environment. We found that specific hydrogen bonds interactions directly involving the chromophore (or not), are correlated to quantities, such as the volume of the cavity in which the chromophore is embedded and that it is importantly affected by the chromophore protonation state. The cross-correlation analysis performed on some of these hydrogen bonds and the cavity volume, demonstrates a direct correlation among them and we also identified the ones specifically involved in this correlation. We also found that specific interactions among residues far in the space are correlated, demonstrating the complexity of the chromophore environment and that many structural quantities have to be taken into account to properly describe and understand the main factors tuning the active site of the protein. From an overall evaluation of the results obtained in this work, it is shown that the residues which a priori are perceived to be spectators play instead an important role in both influencing the chromophore environment (cavity volume) and its dynamics (cross-correlations among spatially distant residues).

Sequence specific hydrogen bond of DNA with denaturants affects its stability: Spectroscopic and simulation studies

BackgroundSeveral different small molecules have been used to target the DNA helix in order to treat the diseases caused by its mutation. Guanidinium(Gdm+) and urea based drugs have been used for the diseases related to central nervous system, also as the anti-inflammatory and chemotherapeutic agent. However, the role of Gdm+ and urea in the stabilization/destabilization of DNA is not well understood. MethodsSpectroscopic techniques along with molecular dynamics (MD) simulation have been performed on different sequences of DNA in the presence of guanidinium chloride (GdmCl) and urea to decode the binding of denaturants with DNA and the role of hydrogen bond with the different regions of DNA in its stability/destability. Results and conclusionOur study reveals that, Gdm+ of GdmCl and urea both intrudes into the groove region of DNA along with the interaction with its phosphate backbone. However, interaction of Gdm+ and urea with the nucleobases in the groove region is different. Gdm+ forms the intra-strand hydrogen bond with the central region of the both sequences of DNA whereas inter-strand hydrogen bond along with water assisted hydrogen bond takes place in the case of urea. The intra-strand hydrogen bond formation capability of Gdm+ with the nucleobases in the minor groove of DNA decreases its groove width which probably causes the stabilization of B-DNA in GdmCl. In contrast, the propensity of the formation of inter-strand hydrogen bond of urea with the nucleobases in the groove region of DNA without affecting the groove width destabilizes B-DNA as compared to GdmCl. This study depicts that the opposite effect of GdmCl and urea on the stability is a general property of B-DNA. However, the extent of stabilization/destabilization of DNA in Gdm+ and urea depend on its sequence probably due to the difference in the intra/inter-strand hydrogen bonding with different bases present in both the sequences of DNA. General significanceThe information obtained from this study will be useful for the designing of Gdm+ based drug molecule which can target the DNA more specifically and selectively.

Investigating dual Ca2+ modulation of the ryanodine receptor 1 by molecular dynamics simulation.

The ryanodine receptors (RyR) are essential to calcium signaling in striated muscles. A deep understanding of the complex Ca2+ -activation/inhibition mechanism of RyRs requires detailed structural and dynamic information for RyRs in different functional states (eg, with Ca2+ bound to activating or inhibitory sites). Recently, high-resolution structures of the RyR isoform 1 (RyR1) were solved by cryo-electron microscopy, revealing the location of a Ca2+ binding site for activation. Toward elucidating the Ca2+ -modulation mechanism of RyR1, we performed extensive molecular dynamics simulation of the core RyR1 structure in the presence and absence of activating and solvent Ca2+ (total simulation time is >5 μs). In the presence of solvent Ca2+ , Ca2+ binding to the activating site enhanced dynamics of RyR1 with higher inter-subunit flexibility, asymmetric inter-subunit motions, outward domain motions and partial pore dilation, which may prime RyR1 for subsequent channel opening. In contrast, the solvent Ca2+ alone reduced dynamics of RyR1 and led to inward domain motions and pore contraction, which may cause inhibition. Combining our simulation with the map of disease mutation sites in RyR1, we constructed a wiring diagram of key domains coupled via specific hydrogen bonds involving the mutation sites, some of which were modulated by Ca2+ binding. The structural and dynamic information gained from this study will inform future mutational and functional studies of RyR1 activation and inhibition by Ca2+ .

Uma nova visão da tripla hélice do DNA: parâmetros estruturais, espectroscópicos e eletrônicos de ligações de hidrogênio para os emparelhamentos de Watson-Crick e Hoogsteen

Através dos cálculos B3LYP/6-31+G(d,p), as estruturas intermoleculares da dupla e tripla hélices do DNA formadas por Timina (T) Adenina (A) foram totalmente otimizadas. Com base na análise de parâmetros estruturais, modos vibracionais e intensidades de absorção no espectro de infravermelho, foram identificadas ligações de hidrogênio entre as bases purina e pirimidina. Pela transferência de carga entre os orbitais de fronteira HOMO e LUMO respectivamente do receptor e doador de prótons, a aplicação dos protocolos NBO e ChElPG proporcionaram resultados insatisfatórios. Todavia, todas as ligações de hidrogênio foram caracterizadas através de descritores QTAIM, pelos quais novos perfis intermoleculares foram obtidos tanto para a dupla (TA) quanto para a tripla (TAT) hélices do DNA.

Structures and NMR spectra of short amylose-lipid complexes. Insight using molecular dynamics and DFT quantum chemical calculations

It is well established that amylose folds in a helix conformation in presence of lipids. Structural features of such molecular complexes are often analysed using 13C NMR spectroscopy. The large size of amylose used to make such analysis doesn't allow to unambiguously correlate structure of polymers and spectroscopic signals. We present structural analysis of small sized amyloses complexed to palmitic acid using classical molecular dynamics. 15 glucoses residues are necessary for the amylose to fold around the palmitic acid in a well-established helix conformation. Simulating 13C NMR spectra using quantum chemical DFT approach, we demonstrate that these spectra are affected by amylose size and specific intramolecular hydrogen bonds. By mean of theoretical NMR spectra of a 19-residues amylose, we precise the attribution of each characteristic resonances. One chemical shift that is usually attributed to a specific carbon may be related to the existence of different inter or intramolecular hydrogen bonds.

Investigating Dual Ca2+ Modulation of the Ryanodine Receptor 1 by Molecular Dynamics Simulation

The ryanodine receptors (RyR) are essential to calcium signaling in striated muscles. A deep understanding of the complex Ca2+ -activation/inhibition mechanism of RyRs requires detailed structural and dynamic information for RyRs in different functional states (eg, with Ca2+ bound to activating or inhibitory sites). Recently, high-resolution structures of the RyR isoform 1 (RyR1) were solved by cryo-electron microscopy, revealing the location of a Ca2+ binding site for activation. Toward elucidating the Ca2+ -modulation mechanism of RyR1, we performed extensive molecular dynamics simulation of the core RyR1 structure in the presence and absence of activating and solvent Ca2+ (total simulation time is >5 μs). In the presence of solvent Ca2+ , Ca2+ binding to the activating site enhanced dynamics of RyR1 with higher inter-subunit flexibility, asymmetric inter-subunit motions, outward domain motions and partial pore dilation, which may prime RyR1 for subsequent channel opening. In contrast, the solvent Ca2+ alone reduced dynamics of RyR1 and led to inward domain motions and pore contraction, which may cause inhibition. Combining our simulation with the map of disease mutation sites in RyR1, we constructed a wiring diagram of key domains coupled via specific hydrogen bonds involving the mutation sites, some of which were modulated by Ca2+ binding. The structural and dynamic information gained from this study will inform future mutational and functional studies of RyR1 activation and inhibition by Ca2+ .

Semi-explicit Solvation Improves Ligand Binding Site Design in an Allosteric Protein

A protein's function is closely derived from its structure; the ability to understand and precisely design structures can thus help create proteins with specific functions. An often-overlooked aspect of protein structural design is the placement of individual water molecules, which are normally approximated as bulk solvent. Previous work has shown that specifying key water molecules improves structural predictions. In particular, designing binding sites in proteins could benefit from modeling waters because the binding affinity and resulting response of proteins to their ligands are influenced by water-mediated hydrogen bonds. Here, we applied solvation to the design of the allosteric transcriptional repressor LacI, with the design goal of inverting the inducibility of both an inducing and anti-inducing ligand. We used a statistical semi-explicit solvation model to solvate LacI; this elucidated specific hydrogen bonds we used to inform our computational redesign of the LacI binding site. We experimentally screened the top six designs to measure their response to various ligands and observed a variety of altered responses compared to wild type; a future challenge is to pinpoint the interactions responsible for the observed allosteric effects. Altogether, our results indicate that considering semi-explicit waters yields greater insight into ligand-protein interactions and can improve current protein design protocols.

Screening of functional monomers and solvents for the molecular imprinting of paclitaxel separation: a theoretical study.

The interactions between the template molecule paclitaxel (PTX) and seven functional monomers containing methacrylic acid (MA), acrolein (AC), 4-vinylbenzoic acid (4VA), acrylonitrile (AN), 2-vinylpyridine (2VP), 2,6-bisacrylamide pyridine (BAP) and methyl methacrylate (MM) were systematically investigated adopting the density functional theory (DFT) method. Moreover, the different binding sites on PTX and solvents embracing chloroform, acetone, ethanol, methanol, and acetonitrile were considered. The calculated solvent energies (ΔEsolvent) and template-monomer binding energies (ΔEb) suggest that the chloroform is the most suitable solvent for the molecular imprinting reaction of PTX among the studied five solvents. Furthermore, from the obtained ΔEb, we can find that the monomer 4VA combining with PTX in the form of the specific intermolecular hydrogen bonds would present the most stable structure among the investigated monomers. These results can provide valuable theoretical guidance for the efficient extraction of PTX by the molecular imprinting technique in experiments. Graphical abstracts.

DNA:chitosan complex, known as a drug delivery system, can create a porous scaffold

Supramolecular structure can be formed using noncovalent interactions based on the self-assembly processes. DNA is a good example for supramolecular materials because it is able to form supramolecular structure by forming specific hydrogen bonds between its base pairs. Moreover, DNA as an anionic medium can bind with oppositely charged materials to form complex structures of various shapes and properties. This work is focused on a foam complex that is formed between negatively charged DNA and positive chitosan. Various characterizations —Fourier transformed infrared spectroscopy (FTIR), Small and Wide-angle X-ray scattering (SAXS and WAXS), scanning electron microscope (SEM), texture analyzer and differential scanning calorimetry (DSC) — are used to study the properties of this dried scaffold. The FTIR spectra presented the chemical structure of DNA and chitosan. While the SAXS power law decay has revealed that an increasing of chitosan content smoothens the surface of the structure, on the other hand, the roughness is much higher when the DNA content is increased. The melting point of the foam from the DSC scan has been identified. The mechanical property of foam is suitable for the application of scaffold, and there is no cytotoxicity of foam to the cell. It is expected that this type of biomaterial could be used in several applications such as functional material and as a drug delivery material.

One Hundred Years After the Latimer and Rodebush Paper, Hydrogen Bonding Remains an Elephant!

Latimer and Rodebush (J Am Chem Soc 42: 1419–1433, 1920) discussed the ways a Lewis dot structure could be drawn for liquid water and proposed that the H held between two octets constitutes a bond in 1920. When it was realized that the other molecule of life, DNA, owes its double helix structure to specific hydrogen bonds between A–T (two) and C–G (three) base pairs, the interest in hydrogen bonding grew dramatically. While hydrogen bonding could be readily seen in water and DNA, it was not so easy to understand leading to continuous debates about what it means. This article gives a personal perspective of the evolution of hydrogen bonding since the Latimer and Rodebush paper to the recent IUPAC definition of hydrogen bond, published in 2011 and now. Is there a third C–H···O hydrogen bond in the A–T base pair?

Cross-linked cellulose nano-sponges: a small angle neutron scattering (SANS) study

Cellulose nano-sponges (CNS), obtained by cross-linking TEMPO oxidized and ultra-sonicated cellulose nano-fibers (TOUS-CNFs) with branched polyethyleneimine (bPEI), underwent here a systematic small angle neutron scattering investigation, by varying the amount of cross-linker and the water content. The aim was to provide experimental evidence of nano-porosity in the TOUS-CNF network of these nano-sponges (CNSs) by investigating the water nano-confinement geometries in the adsorbent material. Moreover, we also verified how the breaking/reformation of specific intermolecular hydrogen bond interactions between water and the chemical groups present in the architecture of the CNSs could contribute to regulate the water adsorption process observed at macroscopic level. The analysis of the experimental data, performed in terms of the correlation length model, allowed us to extract the short-range correlation length ξ, interpreted as a very first indirect estimation of the effective nano-dimension of the cavities produced by the cross-linking of the reticulated cellulose nano-fibers. From the model, power-law (n) and Lorentzian (m) exponents have been also obtained, associated with the density of TOUS-CNFs at high (larger than hundreds of A) and low (~ 10–100 A) spatial scales, respectively. These parameters were all sensitive to the structural variations induced by the progressive uptake of water on the bPEI/TOUS-CNF sponges with different bPEI:TOUS-CNF (w/w) ratios. Finally, we investigated the effect of the addition of citric acid in the CNS formulation, confirming its role in increasing cross-linking density and sponge rigidity. The obtained results appear crucial in order to rationalize the design of these sponges and to track the changes in the ability of the final products as efficient nano-confinement systems for water.

Induced α,γ‐cyclic peptide rotodimer recognition by nucleobase scaffolds

AbstractThe β‐sheet‐type structures derived from the stacking of α,γ‐cyclic peptides to form peptides nanotubes can provide different topoisomers, nonequivalent cyclic peptide stacks generated by the relative rotation through the channel axis of one cyclic peptide with respect to the next component. This rotation generates a series of cyclic peptide dimers paired by the same type of hydrogen bond pattern but differentiated by the cross‐strand side chain‐side chain pairwise. The control of this peptide‐peptide relative orientation in stacked supramolecular aggregates is required for practical applications in material sciences, sensing, or biology. We propose the use of small oligonucleotides to control the prevalence of a particular dimer through the formation of specific hydrogen bonds between cyclic peptides bearing a nucleobase attached to a serine side chain with a complementary oligonucleotide (peptide nucleic acid).

Structural mechanisms underlying activation of TRPV1 channels by pungent compounds in gingers.

Like chili peppers, gingers produce pungent stimuli by a group of vanilloid compounds that activate the nociceptive transient receptor potential vanilloid 1 (TRPV1) ion channel. How these compounds interact with TRPV1 remains unclear. We used computational structural modelling, functional tests (electrophysiology and calcium imaging), and mutagenesis to investigate the structural mechanisms underlying ligand-channel interactions. The potency of three principal pungent compounds from ginger -shogaol, gingerol, and zingerone-depends on the same two residues in the TRPV1 channel that form a hydrogen bond with the chili pepper pungent compound, capsaicin. Computational modelling revealed binding poses of these ginger compounds similar to those of capsaicin, including a "head-down tail-up" orientation, two specific hydrogen bonds, and important contributions of van der Waals interactions by the aliphatic tail. Our study also identified a novel horizontal binding pose of zingerone that allows it to directly interact with the channel pore when bound inside the ligand-binding pocket. These observations offer a molecular level explanation for how unique structures in the ginger compounds affect their channel activation potency. Mechanistic insights into the interactions of ginger compounds and the TRPV1 cation channel should help guide drug discovery efforts to modulate nociception.

Molecular Hydration of Carbonic Acid: Ab Initio Quantum Chemical and Density Functional Theory Investigation.

Molecular hydration of carbonic acid (H2CO3) is investigated in terms of bonding patterns in H2CO3···(H2O) n [ n = 1-4] hydrogen-bonded clusters within ab initio quantum chemical and density functional theory (DFT) frameworks. Successive addition of water molecules to H2CO3···H2O entails elongation of O-H (hydroxyl) bond as well as contraction of specific intermolecular hydrogen bonds signifying hydration of carbonic acid; these structural features get markedly enhanced under the continuum solvation framework. A comparison between the structurally similar clusters H2CO3···(H2O) n and HCOOH···(H2O) n [ n = 1-3] brings out the structural stability of the former. The present investigation in conjunction with the binding energy behavior of approaching water molecule(s) should serve as a precursor for pathways exploring aqueous dissociation of H2CO3 for larger clusters, as well as development of force-field potentials for acid dissociation process.

An Electrochemical Sensor for Disease Diagnosis and Decision Making By Passively Monitoring Chloride Ion Levels in Human Sweat

The human body has a crucial responsibility of maintaining a homeostatic electrolytic balance in body fluids. The inability to do so, is often reflective of an underlying pathophysiology which can be both acute or chronic. One such relevant biomarker is the sweat electrolyte, chloride ion. Human sweat is an easily accessible body fluid which is particularly useful for capturing a physiological snapshot of the biofluid composition, especially when frequent probing is needed. Abnormality in sweat chloride concentrations can be indicative of lethal genetic disorders like Cystic Fibrosis or other less severe conditions of hypo or hyperchloremia like dehydration. It is known that certain acute pathologies like dehydration induce a transient departure in biomarker values from their standard healthy homeostatic ranges. By gauging the deviation of a reference electrolyte levels, such as chloride, the fluctuation in the target disease biomarker levels due the actual chronic disorder can be decoupled from that due to the transient dehydrated state. This work proposes a universal, impedance based, electrochemical biosensor that is capable of monitoring chloride ion levels in sweat that can have implications for all the above-mentioned scenarios. The proposed biosensor is based on the affinity capture of chloride ion levels by a novel, chloride ionophore based immune-assay like sensor stack. The sensor can monitor sweat chloride levels reliably and accurately over the entire physiologically relevant sweat pH range (2 to 8) in ultra-low volumes (1-3mL) of human sweat. The electrochemical sensor is universal as it can be tailored to cater to a gamut of diseases associated with chloride level fluctuations and is passively addressable meaning that it does not rely on active stimulation of the eccrine sweat glands by electrical, chemical or exercise-induced stimulation. This greatly reduces the challenges of sample contamination and evaporation by eliminating the issue of handling large sample volumes. The sensor functions as a two-electrode system with gold working and counter/ reference electrodes deposited onto a flexible, hydrophilic substrate. The capture probe, consisting of the chloride ionophore, 4,5-Bis-[N′-(butyl)thioureido]-2,7-di-tert-butyl-9,9-dimethylxanthene, is bound to the electrodes by way of the crosslinker, DSP (dithiobis (succinimidyl propionate or Lomant’s reagent). The ingress of the chloride ions in the interfacial region of the electrode and the electrolyte and their subsequent capture by the ionophore induces a variation in the electrical double layer parameter values as a function of the ion levels. The affinity capture of the chloride ions is achieved by way of highly specific and strong multitopic hydrogen bonds between the donor(ionophore) and the acceptors( chloride ions), which is afforded owing to the highly preorganized bis-thiourea receptors based on a xanthene spacer, in the suitable chemical structure of the capture probe. The modulation in the electrical double layer and the associated Randle’s circuit parameters, like charge transfer resistance, double layer capacitance and solution resistance, in response to the sweat chloride concentration were transduced to relative impedance changes that were quantified by two powerful AC and DC based electroanalytical techniques of Non-faradaic Electrochemical Impedance Spectroscopy (EIS) and Chronoamperometry (CA) respectively. The calibration dose responses obtained from both the methods were linear with an R2 value> 0.95 for a linear dynamic range of sweat chloride of 10-100mM with a limit of detection of 10mM for the entire sweat pH range of 2 to 8. The chloride sensing scheme is envisioned to be incorporated as point-of-care or wearable diagnostic device when coupled with IOT or Machine Learning modalities for real time monitoring of sweat electrolytes. As evidenced by its flexibility and the immunity of sensor readout to bending and ambulation, the sensor shows good potential to be used as a dynamic hydration sensor for real time monitoring of chloride ions levels in sportspersons and athletes during a game or while on the field. The accuracy and passive addressability of the sensor make it viable at-home diagnostic tool for tracking chloride levels in CF patients for checking the efficacy of on-going treatments, making medical decisions and planning visits to the Doctor’s clinic, by reducing, to some extent, the emotional, financial and psychological stress of the individuals. When incorporated within a combinatorial sensing system, the proposed sensor can reduce false positives of disease diagnosis by acting as a precise yardstick for benchmarking levels of other relevant disease biomarkers also coexisting in the sweat sample. Thus, the proposed chloride sensor can be suitably tailored to universally cater to a plethora of disease diagnostic needs thereby improving the quality of human health by empowering patients to make better informed personalized medical decisions.

TmAFP Interaction with an Ice Lattice

The mealworm beetle, Tenebrio molitor, has an antifreeze protein (TmAFP), which keeps it from freezing solid in sub‐zero temperatures. TmAFP prevents the growth of ice crystals by using repeating coils of a highly conserved 12‐amino acid loop sequence to bind to the ice surface. This structure creates a regular array of threonine‐residues which form specific hydrogen bonds with the ice lattice. As a small protein (8.4 kDa) with this repeating structure, TmAFP is among the simplest AFP structures to be crystallized. This structural simplicity may make it the perfect candidate to use as a tool in prolonging organs that have been harvested for transplant. A current problem is that organs are only viable for transplant for a day at the most. The best way to keep organs viable for prolonged periods of time would be to store them at freezing temperatures. However, if the organ freezes, ice crystals will kill cells and destroy the tissue. By introducing antifreeze proteins into organs before harvesting, the hope is to extend the lifespan of the organ for transplantation. The Ashbury College MSOE Center for BioMolecular Modeling SMART Team used 3D modeling and printing technology to examine structure‐function relationships between TmAFP and ice formation.Support or Funding InformationMSOE ‐ Center for Biomolecular Modelling ‐ co‐sponsor Diane MunzenmaierThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.