The Structural Basis of the Binding of Various Aminopolycarboxylates by the Periplasmic EDTA-Binding Protein EppA from Chelativorans sp. BNC1.

The widespread use of synthetic aminopolycarboxylates, such as ethylenediaminetetraacetate (EDTA), as chelating agents has led to their contamination in the environment as stable metal-chelate complexes. Microorganisms can transport free EDTA, but not metal-EDTA complexes, into cells for metabolism. An ABC-type transporter for free EDTA uptake in Chelativorans sp. BNC1 was investigated to understand the mechanism of the ligand selectivity. We solved the X-ray crystal structure of the periplasmic EDTA-binding protein (EppA) and analyzed its structure-function relations through isothermal titration calorimetry, site-directed mutagenesis, molecular docking, and quantum chemical analysis. EppA had high affinities for EDTA and other aminopolycarboxylates, which agrees with structural analysis, showing that its binding pocket could accommodate free aminopolycarboxylates. Further, key amino acid residues involved in the binding were identified. Our results suggest that EppA is a general binding protein for the uptake of free aminopolycarboxylates. This finding suggests that bacterial cells import free aminopolycarboxylates, explaining why stable metal-chelate complexes are resistant to degradation, as they are not transported into the cells for degradation.

Structure and Function of the Cytochrome P450 Monooxygenase Cinnamate 4-hydroxylase from Sorghum bicolor.

Cinnamate 4-hydroxylase (C4H; CYP73A) is a cytochrome P450 monooxygenase associated externally with the endoplasmic reticulum of plant cells. The enzyme uses NADPH-cytochrome P450 reductase as a donor of electrons and hydroxylates cinnamic acid to form 4-coumaric acid in phenylpropanoid metabolism. In order to better understand the structure and function of this unique class of plant P450 enzymes, we have characterized the enzyme C4H1 from lignifying tissues of sorghum (Sorghum bicolor), encoded by Sobic.002G126600 Here we report the 1.7 Å resolution crystal structure of CYP73A33. The obtained structural information, along with the results of the steady-state kinetic analysis and the absorption spectroscopy titration, displays a high degree of similarity of the structural and functional features of C4H to those of other P450 proteins. Our data also suggest the presence of a putative allosteric substrate-binding site in a hydrophobic pocket on the enzyme surface. In addition, comparing the newly resolved structure with those of well-investigated cytochromes P450 from mammals and bacteria enabled us to identify those residues of critical functional importance and revealed a unique sequence signature that is potentially responsible for substrate specificity and catalytic selectivity of C4H.

Structural and biochemical characterization of iminodiacetate oxidase from Chelativorans sp. BNC1.

Ethylenediaminetetraacetate (EDTA) is the most abundant organic pollutant in surface water because of its extensive usage and the recalcitrance of stable metal-EDTA complexes. A few bacteria including Chelativorans sp. BNC1 can degrade EDTA with a monooxygenase to ethylenediaminediacetate (EDDA) and then use iminodiacetate oxidase (IdaA) to further degrade EDDA into ethylenediamine in a two-step oxidation. To alleviate EDTA pollution into the environment, deciphering the mechanisms of the metabolizing enzymes is an imperative prerequisite for informed EDTA bioremediation. Although IdaA cannot oxidize glycine, the crystal structure of IdaA shows its tertiary and quaternary structures similar to those of glycine oxidases. All confirmed substrates, EDDA, ethylenediaminemonoacetate, iminodiacetate and sarcosine are secondary amines with at least one N-acetyl group. Each substrate was bound at the re-side face of the isoalloxazine ring in a solvent-connected cavity. The carboxyl group of the substrate was bound by Arg265 and Arg307 . The catalytic residue, Tyr250 , is under the hydrogen bond network to facilitate its deprotonation acting as a general base, removing an acetate group of secondary amines as glyoxylate. Thus, IdaA is a secondary amine oxidase, and our findings improve understanding of molecular mechanism involved in the bioremediation of EDTA and the metabolism of secondary amines.

Structural and Functional Characterization of Dynamic Oligomerization in Burkholderia cenocepacia HMG-CoA Reductase.

The enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (HMGR), in most organisms, catalyzes the four-electron reduction of the thioester (S)-HMG-CoA to the primary alcohol (R)-mevalonate, utilizing NADPH as the hydride donor. In some organisms, including the opportunistic lung pathogen Burkholderia cenocepacia, it catalyzes the reverse reaction, utilizing NAD+ as a hydride acceptor in the oxidation of mevalonate. B. cenocepacia HMGR has been previously shown to exist as an ensemble of multiple non-additive oligomeric states, each with different levels of enzymatic activity, suggesting that the enzyme exhibits characteristics of the morpheein model of allostery. We have characterized a number of factors, including pH, substrate concentration, and enzyme concentration, that modulate the structural transitions that influence the interconversion among the multiple oligomers. We have also determined the crystal structure of B. cenocepacia HMGR in the hexameric state bound to coenzyme A and ADP. This hexameric assembly provides important clues about how the transition among oligomers might occur, and why B. cenocepacia HMGR, unique among characterized HMGRs, exhibits morpheein-like behavior.

Hemostatic Comparison of a Polysaccharide Powder and a Gelatin Powder.

Purpose/Aim: Powdered hemostats have been widely adopted for their ease-of-use; however, their efficacy has been limited resulting in applications restricted to low-level bleeds. This study investigates the use of bovine-derived gelatin particles (BGP) as a standalone hemostatic powder and compare BGP to commercially available microporous polysaccharide hemospheres (MPH). Materials and Methods: The powders were investigated for their hemostatic efficacy in a heparinized pre-clinical bleeding model limited to grade 1 and 2 bleeds on a validated intraoperative bleeding scale, which represents the accepted, clinical use of hemostatic powders. Results: At 10 minutes, the hemostatic success of lesions treated with BGP were 78% while MPH were 22%. The odds ratio for hemostatic success of BGP relative to MPH was 15.18 (95% CI: 7.37, 31.27). The 95% lower limit of the odds ratio was greater than 1. This indicates that BGP are superior to MPH (p < 0.001). The median time to hemostasis for BGP was 1.6 minutes and MPH was 14.5 minutes. The ratio for time to hemostasis of MPH relative to BGP was 9.23 (95% CI: 6.99, 12.19). This indicates that BGP achieve significantly faster time to hemostasis (p < 0.001). Conclusions: Characterization of tissue explant ultrastructure, particle size, and swelling revealed differences in the materials. BGP, in addition to absorbing fluid and concentrating clotting factors and platelets, integrate into the clot and stabilize the fibrin matrix. BGP have advantages over MPH in terms of speed and efficacy. BGP are a favorable biomaterial for further research that greatly improve the limited efficacy of powdered hemostats.

Molecular parallelism in fast-twitch muscle proteins in echolocating mammals.

Detecting associations between genomic changes and phenotypic differences is fundamental to understanding how phenotypes evolved. By systematically screening for parallel amino acid substitutions, we detected known as well as novel cases (Strc, Tecta, and Cabp2) of parallelism between echolocating bats and toothed whales in proteins that could contribute to high-frequency hearing adaptations. Our screen also showed that echolocating mammals exhibit an unusually high number of parallel substitutions in fast-twitch muscle fiber proteins. Both echolocating bats and toothed whales produce an extremely rapid call rate when homing in on their prey, which was shown in bats to be powered by specialized superfast muscles. We show that these genes with parallel substitutions (Casq1, Atp2a1, Myh2, and Myl1) are expressed in the superfast sound-producing muscle of bats. Furthermore, we found that the calcium storage protein calsequestrin 1 of the little brown bat and the bottlenose dolphin functionally converged in its ability to form calcium-sequestering polymers at lower calcium concentrations, which may contribute to rapid calcium transients required for superfast muscle physiology. The proteins that our genomic screen detected could be involved in the convergent evolution of vocalization in echolocating mammals by potentially contributing to both rapid Ca2+ transients and increased shortening velocities in superfast muscles.

Clinical effectiveness and versatility of a sealing hemostatic patch (HEMOPATCH) in multiple surgical specialties.

INTRODUCTION: Intraoperative surgical sealants and hemostatic agents have been shown to reduce postoperative complications, transfusions, and hospital resource utilization. Despite availability of these agents, the incidence and burden of bleeding remains high and surgeons' requirements for hemostatic control continue to evolve. A burgeoning class of hemostatic agents are hemostatic patches, which offer package-to-patient readiness and direct application. In addition, hemostatic patches may provide tissue sealing capabilities. Areas covered: This review focuses on the clinical effectiveness, versatility, and surgical efficiency of HEMOPATCH as a surgical sealant and hemostatic agent in various surgical specialties including: cardiac, digestive (hepatic, gastrointestinal, pancreatic), urological, neurological, and endocrine. Expert commentary: Among hemostatic patches, HEMOPATCH is a valuable tool to stop bleeding without adverse events across various surgical specialties. Clinical evidence demonstrates the safety, clinical effectiveness, and versatility of HEMOPATCH as a unique surgical adjunct in patients undergoing complex and routine surgical procedures. Larger randomized-controlled clinical studies, or clinical registries, will continue to be used to evaluate its performance and versatility, particularly for sealing tissues and closing the dura. In the current field of surgical sealing and hemostasis, however, HEMOPATCH represents the next step in improving patient outcomes.

Safety and Efficacy of a Novel, Self-Adhering Dural Substitute in a Canine Supratentorial Durotomy Model.

BACKGROUND: Cerebrospinal fluid (CSF) leaks increase postoperative risk for complication, likelihood of reoperation, and costs. OBJECTIVE: To investigate a novel, self-adhering polyethylene glycol-coated collagen pad (PCC) as a dural substitute relative to Duragen XS (DGX; Integra LifeSciences Corporation, Plainsboro, New Jersey) and as a dural sealant relative to Tachosil (Takeda Austria GmbH, Linz, Austria), a fibrinogen and thrombin-coated collagen pad (FTC). METHODS: A canine supratentorial durotomy surgical model was used to investigate the safety and efficacy of PCC. For safety, 4 animals were bilaterally treated with DGX or PCC and recovered for 1, 8, or 16 wk; total 24 animals. Each animal underwent physical and neurological examinations weekly and 16-wk animals underwent a magnetic resonance imaging (MRI) examination at each time point. For efficacy, 9 animals were unilaterally treated with FTC or PCC and underwent a burst pressure test intraoperatively or 14 d postoperatively; total 36 animals. RESULTS: In the safety study, no abnormal clinical signs or changes were noted on physical and neurological examinations, or in clinical pathology, CSF analysis or histopathology of DGX or PCC-treated animals. No consistent signs of cerebral compression, CSF leak, hemorrhage, or hydrocephalus were noted on MRI. In the efficacy study, no significant difference was found between FTC and PCC at each time point or overall (13.9 vs 12.3 mm Hg, n = 18 per group, P = .46). CONCLUSION: PCC is safe for use as a dural substitute and effective as a dural sealant. The novel, self-adhering combination of a polyethylene glycol-based sealant and a collagen pad may offer unique benefits to the advancement of duraplasty.

Cost-effectiveness analysis of a sealing hemostat patch (HEMOPATCH) vs standard of care in cardiac surgery.

BACKGROUND: A recent randomized controlled trial showed that patients undergoing ascending aorta surgery treated with HEMOPATCH to control bleeding had a significantly better hemostasis success rate than with dry or wet gauze compression or similar standard of care (SOC). OBJECTIVE: To compare the cost-effectiveness using two different agents for hemostasis (HEMOPATCH vs dry or wet gauze compression or similar SOC) in cardiac surgery from the European hospital perspective. METHODS: A literature-based cost-effectiveness model estimating average cost per successful hemostasis event was developed based on the hemostasis efficacy difference (HEMOPATCH = 97.6%, SOC = 65.8%, p < .001). Additional clinically significant end-points studied in the trial (blood transfusions and surgical revisions) were also analyzed. It was assumed that each surgery utilized two units of HEMOPATCH (dimensions of 4.5 × 9 cm) and two units of SOC. Product acquisition costs for HEMOPATCH and SOC were included along with outcome-related costs derived from the literature and inflation-adjusted to 2017 EUR and GBP. Results are presented for an average hospital with an annual case load of 574 cardiac surgeries. One-way and probabilistic sensitivity analyses were performed. RESULTS: Considering only product acquisition cost, HEMOPATCH had an incremental cost-effectiveness ratio (ICER) of €1,659, €1,519, €1,623, and £1,725 per hemostasis success when compared to SOC for Italy, Spain, France, and the UK, respectively. However, when considering the cost and potential difference in the frequency of transfusions and revisions compared to SOC, the use of HEMOPATCH was associated with an annual reduction of six revisions and 60 transfusions, improving the ICER to €1,440, €1,222, €1,461, and £1,592, respectively. Sensitivity analysis demonstrated model robustness. CONCLUSIONS: This analysis supports the use of HEMOPATCH over SOC in cardiac surgery in European hospitals to improve hemostasis success rates and potential cost offsets from reduced transfusions, complications, and surgical revisions.

Building the Class 2 CRISPR-Cas Arsenal.

Adaptation of CRISPR-Cas9 for genome-editing applications has revolutionized biomedical research. New single-component effector CRISPR systems are emerging from the bioinformatics pipeline. How can we best harness their power? Three new studies will no doubt facilitate this transition by generating the C2c1 and C2c2 structure snapshots in different functional states.

Development and validation of an intraoperative bleeding severity scale for use in clinical studies of hemostatic agents.

BACKGROUND: Clinical studies investigating topical hemostatic agents have not used standardized definitions for intraoperative bleeding. The Food and Drug Administration has recently sought use of a validated, clinician-reported scale to standardized bleeding sites in these clinical studies. The intent of a scale is to reduce patient risk, generate labeling claims, and allow comparisons among study results. We describe the development and validation of an intraoperative bleeding severity scale. METHODS: A concept phase defined the framework of the scale. A feasibility and validation phase investigated the usability, clarity, relevance, and reliability (ie, intra- and interobserver concordance) among surgeons and surgical specialties as required by the Food and Drug Administration for the validation of a clinician-reported scale. Data were collected using an online tool. A total of 144 surgeons participated in the 3 phases. RESULTS: The scale developed during the concept phase achieved an average intraobserver concordance of 0.97 and an interobserver concordance of 0.89 in the feasibility phase (N = 33); a concordance of 1.0 is perfect. The scale was refined and then achieved an average intraobserver concordance of 0.98 and an interobserver concordance of 0.91 in the validation phase with unanimous agreement by surgeons from multiple surgical specialties that the scale can be implemented into clinical studies (N = 102). CONCLUSION: This study validated an intraoperative bleeding severity scale for use in clinical studies investigating hemostatic agents. The scale was usable, clear, and clinically relevant with excellent reliability. The scale fulfills requirements of the Food and Drug Administration for a clinician-reported scale and can be used to generate clinically meaningful labeling claims.

Characterization of Class III Peroxidases from Switchgrass.

Class III peroxidases (CIIIPRX) catalyze the oxidation of monolignols, generate radicals, and ultimately lead to the formation of lignin. In general, CIIIPRX genes encode a large number of isozymes with ranges of in vitro substrate specificities. In order to elucidate the mode of substrate specificity of these enzymes, we characterized one of the CIIIPRXs (PviPRX9) from switchgrass (Panicum virgatum), a strategic plant for second-generation biofuels. The crystal structure, kinetic experiments, molecular docking, as well as expression patterns of PviPRX9 across multiple tissues and treatments, along with its levels of coexpression with the majority of genes in the monolignol biosynthesis pathway, revealed the function of PviPRX9 in lignification. Significantly, our study suggested that PviPRX9 has the ability to oxidize a broad range of phenylpropanoids with rather similar efficiencies, which reflects its role in the fortification of cell walls during normal growth and root development and in response to insect feeding. Based on the observed interactions of phenylpropanoids in the active site and analysis of kinetics, a catalytic mechanism involving two water molecules and residues histidine-42, arginine-38, and serine-71 was proposed. In addition, proline-138 and gluntamine-140 at the 137P-X-P-X140 motif, leucine-66, proline-67, and asparagine-176 may account for the broad substrate specificity of PviPRX9. Taken together, these observations shed new light on the function and catalysis of PviPRX9 and potentially benefit efforts to improve biomass conservation properties in bioenergy and forage crops.

Characterization of Post-Translational Modifications to Calsequestrins of Cardiac and Skeletal Muscle.

Calsequestrin is glycosylated and phosphorylated during its transit to its final destination in the junctional sarcoplasmic reticulum. To determine the significance and universal profile of these post-translational modifications to mammalian calsequestrin, we characterized, via mass spectrometry, the glycosylation and phosphorylation of skeletal muscle calsequestrin from cattle (B. taurus), lab mice (M. musculus) and lab rats (R. norvegicus) and cardiac muscle calsequestrin from cattle, lab rats and humans. On average, glycosylation of skeletal calsequestrin consisted of two N-acetylglucosamines and one mannose (GlcNAc2Man1), while cardiac calsequestrin had five additional mannoses (GlcNAc2Man6). Skeletal calsequestrin was not phosphorylated, while the C-terminal tails of cardiac calsequestrin contained between zero to two phosphoryls, indicating that phosphorylation of cardiac calsequestrin may be heterogeneous in vivo. Static light scattering experiments showed that the Ca(2+)-dependent polymerization capabilities of native bovine skeletal calsequestrin are enhanced, relative to the non-glycosylated, recombinant isoform, which our crystallographic studies suggest may be due to glycosylation providing a dynamic "guiderail"-like scaffold for calsequestrin polymerization. Glycosylation likely increases a polymerization/depolymerization response to changing Ca(2+) concentrations, and proper glycosylation, in turn, guarantees both effective Ca(2+) storage/buffering of the sarcoplasmic reticulum and localization of calsequestrin (Casq) at its target site.

Treatment of Severe Aortic Bleeding Using Hemopatch in Swine on Dual Antiplatelet Therapy.

PURPOSE: The perioperative management of patients on antithrombotic therapy is currently an unresolved problem as these therapies pose a considerable risk for perioperative hemorrhagic complications. The presented studies investigated the efficacy of a new collagen technology to achieve hemostasis. A polyethylene glycol-coated collagen pad (PCC) was compared to a marketed fibrinogen-thrombin coated collagen pad (FTC) for the treatment of an aortotomy incision in heparinized swine on dual antiplatelet therapy. MATERIALS AND METHODS: Twenty-eight 3-mm aortotomy incisions were created in nine heparinized pigs without antiplatelet therapy and treated with PCC. Sixty-eight aortotomy incisions were created in ten heparinized pigs that received clopidogrel (10-11 mg/kg) and acetylsalicylic acid (8-11 mg/kg) orally for 5 days, and treated with either PCC or FTC (N = 34/group). Dual antiplatelet therapy resulted in significantly reduced platelet function. Aortotomy incisions resulted in life-threatening bleeding of 35-292 ml/min. RESULTS: In animals without antiplatelet treatment, PCC provided 96% immediate hemostatic success. In animals with antiplatelet treatment, FTC provided 18% immediate hemostatic success increasing to 74% after 10 min. Strikingly, PCC provided 94% immediate success increasing to 100% after 10 min. Controlling for differences in pretreatment bleeding rates, statistical model-estimated time to hemostasis was 12 times shorter in PCC-treated lesions (p < .02). CONCLUSION: The combination of a procoagulant collagen pad with a synthetic sealing component provides excellent hemostatic properties under a worst-case scenario. PCC rapidly and firmly adheres to tissue, thereby controlling severe arterial bleeding, even when platelet function is significantly reduced. Treatment with PCC provided superior time to hemostasis compared to FTC.

Structural and biochemical characterization of EDTA monooxygenase and its physical interaction with a partner flavin reductase.

Ethylenediaminetetraacetate (EDTA) is currently the most abundant organic pollutant due to its recalcitrance and extensive use. Only a few bacteria can degrade it, using EDTA monooxygenase (EmoA) to initiate the degradation. EmoA is an FMNH2 -dependent monooxygenase that requires an NADH:FMN oxidoreductase (EmoB) to provide FMNH2 as a cosubstrate. Although EmoA has been identified from Chelativorans (ex. Mesorhizobium) sp. BNC1, its catalytic mechanism is unknown. Crystal structures of EmoA revealed a domain-like insertion into a TIM-barrel, which might serve as a flexible lid for the active site. Docking of MgEDTA(2-) into EmoA identified an intricate hydrogen bond network connected to Tyr(71) , which should potentially lower its pKa. Tyr(71) , along with nearby Glu(70) and a peroxy flavin, facilitates a keto-enol transition of the leaving acetyl group of EDTA. Further, for the first time, the physical interaction between EmoA and EmoB was observed by ITC, molecular docking and enzyme kinetic assay, which enhanced both EmoA and EmoB activities probably through coupled channelling of FMNH2 .

Computed Tomographic Characterization of Traumastem-A New Oxidized Cellulose Hemostatic Agent.

Oxidized regenerated cellulose (ORC) is a commonly used surgical hemostatic agent. When retained at the surgical site, it is frequently misdiagnosed on postoperative computed tomography (CT) images as an abscess or a recurrent tumor. Oxidized nonregenerated cellulose (ONC) is a new, more effective version of ORC. It is more effective because of its unorganized fiber structure and greater material density, which may also alter its appearance on CT images relative to ORC. This image report compares the CT characteristics of ONC and ORC. A rabbit's bilateral femoral arteries were punctured to model peripheral vascular surgery. ORC was used to treat 1 of the femoral artery punctures and ONC to treat the contralateral puncture. Noncontrast CT imaging was performed immediately following surgery (day 0) and on postoperative day 14. On day 0, both ORC and ONC were isoattenuating relative to muscle and hyperattenuating to fat, although ONC appears more homogenous. On day 14, neither ORC nor ONC was clearly identifiable. Thus, postoperative retention of ONC can obscure immediate postoperative CT interpretation and, similar to ORC, lead to an erroneous diagnosis of an abscess. By day 14, ONC retention may not obscure CT interpretation. In noncontrast CT imaging, ONC appears more homogeneous than ORC, but is otherwise indistinguishable. The greater homogeneity of ONC may be caused by the unorganized fiber structure or greater material density. Intraoperative use of ONC should be clinically investigated before radiographically diagnosing a postoperative abscess or recurrent tumor.

Characterization of Two Human Skeletal Calsequestrin Mutants Implicated in Malignant Hyperthermia and Vacuolar Aggregate Myopathy.

Calsequestrin 1 is the principal Ca(2+) storage protein of the sarcoplasmic reticulum of skeletal muscle. Its inheritable D244G mutation causes a myopathy with vacuolar aggregates, whereas its M87T "variant" is weakly associated with malignant hyperthermia. We characterized the consequences of these mutations with studies of the human proteins in vitro. Equilibrium dialysis and turbidity measurements showed that D244G and, to a lesser extent, M87T partially lose Ca(2+) binding exhibited by wild type calsequestrin 1 at high Ca(2+) concentrations. D244G aggregates abruptly and abnormally, a property that fully explains the protein inclusions that characterize its phenotype. D244G crystallized in low Ca(2+) concentrations lacks two Ca(2+) ions normally present in wild type that weakens the hydrophobic core of Domain II. D244G crystallized in high Ca(2+) concentrations regains its missing ions and Domain II order but shows a novel dimeric interaction. The M87T mutation causes a major shift of the α-helix bearing the mutated residue, significantly weakening the back-to-back interface essential for tetramerization. D244G exhibited the more severe structural and biophysical property changes, which matches the different pathophysiological impacts of these mutations.

Characterizations of Two Bacterial Persulfide Dioxygenases of the Metallo-ß-lactamase Superfamily.

Persulfide dioxygenases (PDOs), also known as sulfur dioxygenases (SDOs), oxidize glutathione persulfide (GSSH) to sulfite and GSH. PDOs belong to the metallo-ß-lactamase superfamily and play critical roles in animals, plants, and microorganisms, including sulfide detoxification. The structures of two PDOs from human and Arabidopsis thaliana have been reported; however, little is known about the substrate binding and catalytic mechanism. The crystal structures of two bacterial PDOs from Pseudomonas putida and Myxococcus xanthus were determined at 1.5- and 2.5-Å resolution, respectively. The structures of both PDOs were homodimers, and their metal centers and ß-lactamase folds were superimposable with those of related enzymes, especially the glyoxalases II. The PDOs share similar Fe(II) coordination and a secondary coordination sphere-based hydrogen bond network that is absent in glyoxalases II, in which the corresponding residues are involved instead in coordinating a second metal ion. The crystal structure of the complex between the Pseudomonas PDO and GSH also reveals the similarity of substrate binding between it and glyoxalases II. Further analysis implicates an identical mode of substrate binding by known PDOs. Thus, the data not only reveal the differences in metal binding and coordination between the dioxygenases and the hydrolytic enzymes in the metallo-ß-lactamase superfamily, but also provide detailed information on substrate binding by PDOs.

Efficacy of hemostatic matrix and microporous polysaccharide hemospheres.

BACKGROUND: Microporous Polysaccharide Hemospheres (MPH) are a new plant-derived polysaccharide powder hemostat. Previous studies investigated MPH as a replacement to nonflowable hemostatic agents of different application techniques (e.g., oxidized cellulose, collagen); therefore, the purpose of this study was to determine if MPH is a surrogate for flowable hemostatic agents of similar handling and application techniques, specifically a flowable thrombin-gelatin hemostatic matrix. METHODS: Hemostatic efficacy was compared using a heparinized porcine abrasion model mimicking a capsular tear of a parenchymal organ. MPH (ARISTA, 1 g) and hemostatic matrix (Floseal, 1 mL) were applied, according to a randomized scheme, to paired hepatic abrasions (40 lesions per group). Hemostatic success, control of bleeding, and blood loss were assessed 2, 5, and 10 min after treatment. Hemostatic success and control of bleeding were analyzed using odds ratios and blood loss using mean differences. RESULTS: Hemostatic matrix provided superior hemostatic success relative to MPH at 5 (odds ratio: 0.035, 95% confidence interval: 0.004-0.278) and 10 min (0.032, 0.007-0.150), provided superior control of bleeding at 5 (0.006, <0.001-0.037) and 10 min (0.009, 0.001-0.051), and had significantly less blood loss at 5 (mean difference: 0.3118 mL/min, 95% confidence interval: 0.0939-0.5296) and 10 min (0.5025, 0.2489-0.7561). CONCLUSIONS: These findings corroborate other MPH investigations regarding its low-level efficacy and suggest that MPH is not an appropriate surrogate for hemostatic matrix despite similar application techniques. The lack of a procoagulant within MPH may likely be the reason for its lower efficacy and need for multiple applications.

Structures of the inducer-binding domain of pentachlorophenol-degrading gene regulator PcpR from Sphingobium chlorophenolicum.

PcpR is a LysR-type transcription factor from Sphingobium chlorophenolicum L-1 that is responsible for the activation of several genes involved in polychlorophenol degradation. PcpR responds to several polychlorophenols in vivo. Here, we report the crystal structures of the inducer-binding domain of PcpR in the apo-form and binary complexes with pentachlorophenol (PCP) and 2,4,6-trichlorophenol (2,4,6-TCP). Both X-ray crystal structures and isothermal titration calorimetry data indicated the association of two PCP molecules per PcpR, but only one 2,4,6-TCP molecule. The hydrophobic nature and hydrogen bonds of one binding cavity allowed the tight association of both PCP (Kd = 110 nM) and 2,4,6-TCP (Kd = 22.8 nM). However, the other cavity was unique to PCP with much weaker affinity (Kd = 70 µM) and thus its significance was not clear. Neither phenol nor benzoic acid displayed any significant affinity to PcpR, indicating a role of chlorine substitution in ligand specificity. When PcpR is compared with TcpR, a LysR-type regulator controlling the expression of 2,4,6-trichlorophenol degradation in Cupriavidus necator JMP134, most of the residues constituting the two inducer-binding cavities of PcpR are different, except for their general hydrophobic nature. The finding concurs that PcpR uses various polychlorophenols as long as it includes 2,4,6-trichlorophenol, as inducers; whereas TcpR is only responsive to 2,4,6-trichlorophenol.