Molecular Weight Classes Research Articles

Ceragenins Prevent the Development of Murine Vaginal Infection Caused by Gardnerella vaginalis

Background/Objectives: Bacterial vaginosis (BV), an infection caused primarily by Gardnerella vaginalis, is the most prevalent vaginal infection. Although BV is often characterized by an asymptomatic course, it can lead to considerable health complications. Currently, BV therapy choices are limited, and available treatments are complicated by concerns about antibiotic resistance. Ceragenins, which together comprise an innovative class of low molecular-weight, cholic acid-based antibacterial agents, have emerged as potential alternatives to conventional treatments. Methods: This study investigates (i) the antibacterial activity of ceragenins against G. vaginalis in in vitro experimental settings at varied pH, and (ii) the effectiveness and anti-inflammatory properties of CSA-13 in a G. vaginalis-induced bacterial vaginosis animal model. Results and Conclusions: We demonstrate that ceragenins, particularly CSA-13, maintain their antibacterial efficacy throughout pH range of 4.5–7, with the highest activity observed at neutral pH (7.0). Additionally, in an animal model, beneficial effects of ceragenins are attributed to anti-inflammatory properties of these compounds, making these compounds promising agents as potential new treatment options against G. vaginalis-associated vaginal infections.

Isolation, purification, characterization, and analysis of the antioxidant activity of antioxidant peptides from walnut milk fermented with Lactobacillus paracasei SMN-LBK

Microbial fermentation is an important method to obtain antioxidant peptides. In this study, Lactobacillus paracasei SMN-LBK was used to ferment biprotein (walnut milk) to enhance the antioxidant capacity of the active peptide. The optimal fermentation process of 5% inoculum, 1:7 plant protein ratio, 37 °C and 12 h resulted in 77.63% ± 0.36% DPPH scavenging, 93.31% ± 0.25% ABTS scavenging and 79.37% ± 0.02% metal ion chelating capacity. The hydrolysis products were classified into three molecular weight classes using an ultrafiltration membrane system. DPAP-3 with a molecular weight of less than 3 kDa had the highest antioxidant activity. DPAP-3 was further separated into three subclasses using gel filtration chromatography. These subclasses were characterized using nano-liquid chromatography-tandem mass spectrometry (NanoLC-MS/MS) and screened by searching https://biochemia.uwm.edu. Four antioxidant peptides were identified using a combination of hydrophobic amino acids, positive ion-charge interactions, and numerical values. Two of these peptides were from animals and one from plants. Their amino acid sequences are as follows PCRGVLLR, IHIPLPRWV, QSKVLPVPQK, and KVLPVPQKA, with molecular docking binding energies of −7.8, −8.3, −7.4, and −7.7 kcal/mol, respectively. The results suggest that fermentation of plant-animal proteins with Lactobacillus paracasei can produce antioxidant peptides that can be used as functional ingredients in food products. This has the potential to conserve animal protein resources.

Effect of feed concentration in solvent/anti-solvent precipitation fractionation of lignin: Impact on lignins structure-property correlations

Technical lignins are relatively heterogeneous and structurally not fully understood, which hinders their commercialization. This study involves the precipitation fractionation of organosolv (OS) lignin into different molecular weight (MW) classes by stepwise addition of water as an anti-solvent in acetone/water mixtures with varying feed lignin concentrations of 5, 10, and 15 wt. % in the lignin/solvent/anti-solvent mixture. Characterization of the obtained lignin fractions by SEC-MALS, TM-DSC, and 31P NMR revealed MW classes in a broad range from 2050 to 26500 g mol−1, glass transition temperatures between 68 and 201 °C and the presence of different amounts of hydroxyl groups. The results verify that besides the acetone/water gradient, the lignin concentration has a major influence on the fractionation outcome. We demonstrate the significant impact of different OS lignin concentrations on the solubility of such polydisperse system and hereby establish an additional way to tune the molecular weight of lignin fractions and their related physico-chemical properties.

Morelloflavone as Phytomedicine-An Ethnopharmacological Review on the Therapeutical Properties, Biological Efficacy and Pharmacological Activity

Background:Flavonoids are low molecular weight class secondary metabolites found to be present throughout the plant kingdom. Structurally, flavonoid class phytochemicals consist of C6-C3-C6 chemical structures with different substitution patterns and have drug-like nature. Morelloflavone is a biflavonoid class phytochemical found to be present abundantly in the Garcinia genus. Morelloflavone has been investigated in the scientific field for its numerous pharmacological activities. The present work aims to discuss the scientific progress of health beneficial aspects and pharmacological potential of morelloflavone in medicine.Methods:The purpose of this work is to provide scientific information about the biological potential and health beneficial effects of flavonoids in medicine with special reference to the morelloflavone. In this work, we have collected the scientific data of morelloflavone for the biological potential and pharmacological activities against different types of human illnesses with their mechanism of action from Google, Google Scholar, Science Direct and PubMed and analyzed. Further, the preventive role of morelloflavone against various types of human illnesses and the mechanism of action have also been discussed in the present work. This work will provide upto- date information on the health beneficial aspects of morelloflavone in medicine for the prevention and treatment of human complications.Results:Morelloflavone exhibited a wide-range of pharmacologic activity in regulating numerous kinds of human disorders. Present work revealed the health beneficial aspects and pharmacological activities of morelloflavone for the prevention and treatment of human disorders due to its anti-microbial, anti-plasmodial, anti-oxidant, anti-atherosclerosis, anti-inflammatory, anti-tumor anti-restenosis, anti-HIV, aphrodisiac, anti-Alzheimer's and apoptotic potential in the medicine. Further, its biological potential on phospholipase A2, melanin, kallikreins, monoamine oxidase, aromatase, Eg5 Inhibition and proprotein convertases have been also analyzed in the present work. Analytical data signified the importance of modern analytical tools for the separation and isolation of morelloflavone in medicine.Conclusion:Present work revealed the detailed pharmacological activities of morelloflavone that can be utilized in the future for the development of new pharmacologic agents.

Fractionation and Absolute Molecular Weight Determination of Organosolv Lignin and Its Fractions: Analysis by a Novel Acetone-Based SEC─MALS Method

Accurate and reliable structural characterization of technical lignins is still challenging and inhibits industrial utilization as only poor understanding of structure–property relationship is available. Especially, molar mass analysis of technical lignins is of paramount interest; however, the usage of conventional size exclusion chromatography (SEC) and synthetic polymer standards as a consequence of inaccessible lignin standards is predominantly found in academia. This leads to a huge discrepancy in molecular weight analyses of lignins between different laboratories and consequently to fragile comparability. In this study, organosolv (OS) lignin from beech wood was exemplarily used to develop and evaluate a new acetone–water-based SEC method with the ability to be coupled to an electrospray ionization-mass spectrometer (ESI-MS) or to a multi-angle light scattering detector (MALLS or short MALS). The eluent system used shows very good solubility for the lignins investigated and hence lowers the probability for molecular aggregation of lignin molecules in solution. Solvent fractionation in acetone–water mixtures was conducted to acquire molecular weight classes. The starting lignin (parent lignin) was initially dissolved in 80 wt % acetone–water. Various fractions of the parent lignin were produced by a stepwise reduction of the acetone content. Molecular weights based on narrow polyethylene glycol (PEG)/polyethylene oxide (PEO) standards and absolute molar masses by coupling SEC with MALS were obtained, and the drawback of using polymer standards is discussed in detail. At a lower acetone content, low-molecular-weight fractions were found. Additionally, the specific refractive index increments (dn/dc) were determined for the parent lignin and its fractions. The impact of dn/dc on the final molecular weight (MW) was evaluated considering the chemical composition obtained by nuclear magnetic resonance spectroscopy (NMR) analysis. Furthermore, light scattering revealed that the absorption behavior for this OS lignin is low and neglectable. This article proposes a new acetone-based analytical method for direct determination of absolute molar masses of OS lignin molecules.

Dry Glass Reference Perturbation Theory Predictions of the Temperature and Pressure Dependent Separations of Complex Liquid Mixtures Using SBAD-1 Glassy Polymer Membranes.

In this work we apply dry glass reference perturbation theory (DGRPT) within the context of fully mutualized diffusion theory to predict the temperature and pressure dependent separations of complex liquid mixtures using SBAD-1 glassy polymer membranes. We demonstrate that the approach allows for the prediction of the membrane-based separation of complex liquid mixtures over a wide range of temperature and pressure, using only single-component vapor sorption isotherms measured at 25 °C to parameterize the model. The model was then applied to predict the membrane separation of a light shale crude using a structure oriented lumping (SOL) based compositional model of petroleum. It was shown that when DGRPT is applied based on SOL compositions, the combined model allows for the accurate prediction of separation performance based on the trend of both molecular weight and molecular class.

Segmented Polyurethanes and Thermoplastic Elastomers from Elemental Sulfur with Enhanced Thermomechanical Properties and Flame Retardancy

AbstractThe production of elemental sulfur from petroleum refining has created a technological opportunity to increase the valorization of elemental sulfur by the creation of high‐performance sulfur based plastics with improved thermomechanical properties, elasticity and flame retardancy. We report on a synthetic polymerization methodology to prepare the first example of sulfur based segmented multi‐block polyurethanes (SPUs) and thermoplastic elastomers that incorporate an appreciable amount of sulfur into the final target material. This approach applied both the inverse vulcanization of S8 with olefinic alcohols and dynamic covalent polymerizations with dienes to prepare sulfur polyols and terpolyols that were used in polymerizations with aromatic diisocyanates and short chain diols. Using these methods, a new class of high molecular weight, soluble block copolymer polyurethanes were prepared as confirmed by Size Exclusion Chromatography, NMR spectroscopy, thermal analysis, and microscopic imaging. These sulfur‐based polyurethanes were readily solution processed into large area free standing films where both the tensile strength and elasticity of these materials were controlled by variation of the sulfur polyol composition. SPUs with both high tensile strength (13–24 MPa) and ductility (348 % strain at break) were prepared, along with SPU thermoplastic elastomers (578 % strain at break) which are comparable values to classical thermoplastic polyurethanes (TPUs). The incorporation of sulfur into these polyurethanes enhanced flame retardancy in comparison to classical TPUs, which points to the opportunity to impart new properties to polymeric materials as a consequence of using elemental sulfur.

Optimization of Headspace Solid-phase Microextraction for the Analysis of Volatile Compounds of High-fat Dairy Powders

Optimization of main extraction parameters of the headspace solid-phase microextraction (SPME) method for two high-fat dairy powders with distinctly different volatile profiles was performed with response surface methodology. While cream powder (60% fat content) has a weak odor, enzyme-modified cheese powder (EMC) (35% fat content) is known with its intense flavor generated by high degrees of proteolysis and lipolysis. Extraction time, extraction temperature, and agitation speed were selected as optimization factors. Eight different volatile compounds isolated from cream powder and ten volatiles detected in EMC powder in varied molecular weight, boiling temperature, and organic classes were selected as optimization responses to express the overall extraction efficiency and volatile profile of powders. Optimization was performed to obtain the highest extraction efficiency for each response. It is suggested to use the SPME conditions at 56.2 °C for 70.8 min with 250 rpm for the isolation of volatiles in cream powder whereas the extraction temperature, time, and agitation speed were optimized for EMC powders as 53.4 °C, 63.2 min, and 250, respectively.

Engineered Alginate Microcapsules for Molecular Therapy Through Biologic Secreting Cells.

Continuous delivery of monoclonal antibodies (mAbs) at low concentrations may be helpful in the management of several chronic, especially autoimmune diseases. A possible approach to employ mAbs therapy in vivo, in the absence of in vitro manipulations, could be graft of microcapsules containing mAb-secreting hybridoma cells (HY). Sodium alginate (AG) is a polymeric saccharide that permits simple fabrication of microcapsules that are biocompatible and prevent immune recognition of encapsulated cells, upon graft, by the host's immune system. However, at present, AG-based microcapsules are usually impermeable to large molecules. The aim of this study was to engineer the membrane of AG-based microcapsules, to make it permeable to larger molecular weight classes of mAbs. To this end, we have prepared a new AG-based membrane, using standard reagents already in use, but following different coating procedures and molar ratios. In particular, we fabricated a new capsular membrane permeable to IgM synthesized by the HY cell line, G3C. Morphologic structural and ultrastructural analysis of the new membranes before and after intraperitoneal transplant, in conjunction with IgM outflow secretory kinetics underwent both, in vitro and in vivo assessments. While allowing immunoprotection of the enveloped HY, as demonstrated by the absence of any inflammatory response, the microcapsules permitted G3c mAb egress, on a regulated delivery kinetics. HY viability persisted, upon transplant, for long time periods. In summary, the new AG-based microcapsules allow delivery of big molecules out of the capsules, while protecting the enveloped HY from the host's immune system. These microcapsules could apply to implant cells producing fully active large molecules without the need of time- and cost expensive procedures to purify them.

Characterization of putative DD-carboxypeptidase-encoding genes in Mycobacterium smegmatis

Penicillin binding proteins (PBPs) are the target of numerous antimicrobial agents that disrupt bacterial cell wall synthesis. In mycobacteria, cell elongation occurs through insertion of nascent cell wall material in the sub-polar region, a process largely driven by High Molecular Weight PBPs. In contrast, the function of DD-carboxypeptidases (DD-CPases), which are Low Molecular Weight Class 1C PBPs, in mycobacteria remains poorly understood. Mycobacterium smegmatis encodes four putative DD-CPase homologues, which display homology to counterparts in Escherichia coli. Herein, we demonstrate that these are expressed in varying abundance during growth. Deletion of MSMEG_1661, MSMEG_2433 or MSMEG_2432, individually resulted in no defects in growth, cell morphology, drug susceptibility or spatial incorporation of new peptidoglycan. In contrast, deletion of MSMEG_6113 (dacB) was only possible in a merodiploid strain expressing the homologous M. tuberculosis operon encoding Rv3627c (dacB), Rv3626c, Rv3625c (mesJ) and Rv3624c (hpt), suggestive of essentiality. To investigate the role of this operon in mycobacterial growth, we depleted gene expression using anhydrotetracycline-responsive repressors and noted reduced bipolar peptidoglycan synthesis. These data point to a possible role for this four gene operon, which is highly conserved across all mycobacterial species, in regulating spatial localization of peptidoglycan synthesis.

Dissolved and colloidal copper in the tropical South Pacific

Copper (Cu) as a bioactive trace metal in the ocean has widely been studied in the context of chemical speciation. However, this trace metal is extremely understudied in the context of physical speciation (i.e., size- or molecular weight-partitioning), which may help in characterizing dissolved Cu species. In this study, we determine total dissolved Cu (<0.2 μm) distribution and its physical speciation along the US GEOTRACES 2013 cruise, a 4300-km east-west transect in the tropical South Pacific. The distribution of dissolved Cu is rather uniform horizontally and exhibits a linear increase with depth from surface to 2500–3000 m, below which it varies less significantly both vertically and horizontally. Dissolved Cu shows a strong correlation with silicate (SiO44−) in the upper 1500 m, which is in agreement with previous studies in other regions. This correlation is weaker but with higher slope at depths below 1500 m, which supports the sedimentary source hypothesis. Although hydrothermal activity at the East Pacific Rise (EPR) does not show a readily evident impact on the dissolved Cu distribution, high-quality data at 2300–2800 m allow for diagnosing a subtle westward decrease in the background-subtracted dissolved Cu component. This component of dissolved Cu poorly correlates with mantle-derived 3He (R2 = 0.41), indicating a possible hydrothermal source for dissolved Cu, in contrast to previous studies. For the first time in a major basin, we also determined the physical speciation of dissolved Cu, which shows that Cu species lighter than 10 kDa (Da = 1 g mol−1) dominate the pool of dissolved Cu (<0.2 μm) below 1000 m with a contribution of 61 ± 6% (fraction of total dissolved). 39 ± 6% of dissolved Cu at depths below 1000 m, thus, occurs in the pool of colloidal matter (10 kDa–0.2 μm). Moreover, using a suite of molecular weight cutoffs indicate that Cu species are distributed between two distinct molecular weight classes: the lighter than 5 kDa and heavier than 300 kDa classes, which form 53 ± 6% and 37 ± 7% of dissolved Cu at 2200–2800 m, respectively. The Cu species with molecular weight between 5 kDa and 300 kDa contribute only to 10 ± 12% of the pool at 2200–2800 m. These results offer new insights into structure, reactivity and bioavailability of oceanic Cu compounds. As an organic-dominating metal, Cu physical speciation may also shed light on size-reactivity spectrum of dissolved organic matter (DOM) in the deep ocean.

Sources, compositions, and optical properties of humic-like substances in Beijing during the 2014 APEC summit: Results from dual carbon isotope and Fourier-transform ion cyclotron resonance mass spectrometry analyses

Humic-like substances (HULIS) are a class of high molecular weight, light-absorbing compounds that are highly related to brown carbon (BrC). In this study, the sources and compositions of HULIS isolated from fine particles collected in Beijing, China during the 2014 Asia-Pacific Economic Cooperation (APEC) summit were characterized based on carbon isotope (13C and 14C) and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses, respectively. HULIS were the main light-absorbing components of water-soluble organic carbon (WSOC), accounting for 80.2 ± 6.1% of the WSOC absorption capacity at 365 nm. The carbon isotope data showed that HULIS had a lower non-fossil contribution (53 ± 4%) and were less enriched with 13C (−24.2 ± 0.6‰) relative to non-HULIS (62 ± 8% and −20.8 ± 0.3‰, respectively). The higher relative intensity fraction of sulfur-containing compounds in HULIS before and after APEC was attributed to higher sulfur dioxide levels emitted from fossil fuel combustion, whereas the higher fraction of nitrogen-containing compounds during APEC may have been due to the relatively greater contribution of non-fossil compounds or the influence of nitrate radical chemistry. The results of investigating the relationships among the sources, elemental compositions, and optical properties of HULIS demonstrated that the light absorption of HULIS appeared to increase with increasing unsaturation degree, but decrease with increasing oxidation level. The unsaturation of HULIS was affected by both sources and aging level.

Comprehensive Analysis of Changes in Crude Oil Chemical Composition during Biosouring and Treatments.

Biosouring in crude oil reservoirs by sulfate-reducing microbial communities (SRCs) results in hydrogen sulfide production, precipitation of metal sulfide complexes, increased industrial costs of petroleum production, and exposure issues for personnel. Potential treatment strategies include nitrate or perchlorate injections into reservoirs. Gas chromatography with vacuum ultraviolet ionization and high-resolution time-of-flight mass spectrometry (GC-VUV-HTOF) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) combined with electrospray ionization were applied in this study to identify hydrocarbon degradation patterns and product formations in crude oil samples from biosoured, nitrate-treated, and perchlorate-treated bioreactor column experiments. Crude oil hydrocarbons were selectively transformed based on molecular weight and compound class in the biosouring control environment. Both the nitrate and the perchlorate treatments significantly reduced sulfide production; however, the nitrate treatment enhanced crude oil biotransformation, while the perchlorate treatment inhibited crude oil biotransformation. Nitrogen- and oxygen-containing biodegradation products, particularly with chemical formulas consistent with monocarboxylic and dicarboxylic acids containing 10-60 carbon atoms, were observed in the oil samples from both the souring control and the nitrate-treated columns but were not observed in the oil samples from the perchlorate-treated column. These results demonstrate that hydrocarbon degradation and product formation of crude oil can span hydrocarbon isomers and molecular weights up to C60 and double-bond equivalent classes ranging from straight-chain alkanes to polycyclic aromatic hydrocarbons. Our results also strongly suggest that perchlorate injections may provide a preferred strategy to treat biosouring through inhibition of biotransformation.

Proteomics Investigations into Serum Proteins Adsorbed by High-Flux and Low-Flux Dialysis Membranes.

Hemodialysis is one of the most important therapies for patients with uremia, and the dialysis membrane is the predominant factor that impacts the efficiency of dialysis. Here, a protein adsorption on two different membranes is investigated to provide a basis for improving dialysis materials. Two cases treated with the Polyflux 14L low-flux dialyzer and the Polyflux 140H high-flux dialyzers during two continuous therapies are selected. Four used dialyzers from selected patients are infused with C12Im-Cl to elute the adsorbed proteins. Then labeled digested proteins adsorb by Polyflux 140H and Polyflux 14L with 13 CD2 O and NaCNBD3 (light labeling, L) and CD2 O and NaCNBH3 (heavy labeling, H), respectively. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is used to identify the proteins. According to the ratio (Light labeling/Heavy labeling), the eluted proteins are divided into three groups: significantly higher, significantly lower, and no significant differences with a ratio of >2, <0.5, and 0.5-2, respectively. A total of 668 proteins are identified by LC-MS/MS, among which 177 proteins are retained more by the Polyflux 140H membrane (ratio >2), 320 proteins are retained more by the Polyflux 14L membrane (ratio <0.5), and 171 proteins show no significant difference (ratio 0.5-2) between the two types of membranes. Statistical significance is shown in the percentage of adsorbed proteins with an isoelectric point (pI) ranging from 9 to 10 (19.08 versus 7.69%; χ2 = 11.87, p = 0.0006). Proteins with a molecular weight (MW) of 10-15 kDa tend to deposit on Polyflux 140H compared with Polyflux 14L (25 versus 9.23%; χ2 = 18.66, p = 0.0000) and proteins with a MW of 30-60 kDa tend to deposit on Polyflux 14L compared with Polyflux 140H (36.54 versus 22.37%; χ2 = 8.96, p = 0.0028). According to gene ontology analysis, the proteins adsorbed by dialysis membranes are closely related to activation of complement system and the coagulation cascade. The proteins adsorbed by Polyflux 140H and Polyflux 14L show significant differences in PI, MW, and protein class. Proteomic techniques are an effective approach for studying hemodialysis membranes.

Copper metallothioneins.

Metallothioneins (MTs) are a class of low molecular weight and cysteine-rich metal binding proteins present in all the branches of the tree of life. MTs efficiently bind with high affinity several essential and toxic divalent and monovalent transition metals by forming characteristic polynuclear metal-thiolate clusters within their structure. MTs fulfil multiple biological functions related to their metal binding properties, with essential roles in both Zn(II) and Cu(I) homeostasis as well as metal detoxification. Depending on the organism considered, the primary sequence, and the specific physiological and metabolic status, Cu(I)-bound MT isoforms have been isolated, and their chemistry and biology characterized. Besides the recognized role in the biochemistry of divalent metals, it is becoming evident that unique biological functions in selectively controlling copper levels, its reactivity as well as copper-mediated biochemical processes have evolved in some members of the MT superfamily. Selected examples are reviewed to highlight the peculiar chemical properties and biological functions of copper MTs. © 2016 IUBMB Life, 69(4):236-245, 2017.

Microvasculature of the Mouse Cerebral Cortex Exhibits Increased Accumulation and Synthesis of Hyaluronan With Aging.

The microvasculature of the aged brain is less dense and more vulnerable to dysfunction than that of the young brain. Brain microvasculature is supported by its surrounding extracellular matrix, which is comprised largely of hyaluronan (HA). HA is continually degraded into lower molecular weight forms that induce neuroinflammation. We examined HA associated with microvessels (MV) of the cerebral cortex of young (4 months), middle-aged (14 months), and aged (24-26 months) mice. We confirmed that the density of cortical MV decreased with age. Perivascular HA levels increased with age, but there was no age-associated change in HA molecular weight profile. MV isolated from aged cortex had more HA than MV from young cortex. Examination of mechanisms that might account for elevated HA levels with aging showed increased HA synthase 2 (HAS2) mRNA and protein in aged MV relative to young MV. In contrast, mRNAs for HA-degrading hyaluronidases or hyaladherins that mitigate HA degradation showed no changes with age. Corresponding to increased HAS2, aged MV synthesized significantly more HA (of all molecular weight classes) in vitro than young MV. We propose that increased HA synthesis and accumulation in brain MV contributes to neuroinflammation and reduced MV density and function in aging.

Plant antiherbivore defenses in Fabaceae species of the Chaco.

The establishment and maintenance of plant species in the Chaco, one of the widest continuous areas of forests in the South American with sharp climatic variations, are possibly related to biological features favoring plants with particular defenses. This study assesses the physical and chemical defenses mechanisms against herbivores of vegetative and reproductive organs. Its analyses of 12 species of Fabaceae (Leguminosae) collected in remnants of Brazilian Chaco shows that 75% present structural defense characters and 50% have chemical defense - defense proteins in their seeds, like protease inhibitors and lectins. Physical defenses occur mainly on branches (78% of the species), leaves (67%), and reproductive organs (56%). The most common physical characters are trichomes and thorns, whose color represents a cryptic character since it does not contrast with the other plant structures. Defense proteins occur in different concentrations and molecular weight classes in the seeds of most species. Protease inhibitors are reported for the first time in seeds of: Albizia niopoides, Anadenanthera colubrina, Mimosa glutinosa, Prosopis rubriflora, and Poincianella pluviosa. The occurrence of physical and chemical defenses in members of Fabaceae indicate no associations between defense characters in these plant species of the Chaco.

Small associative molecule thickeners for ethane, propane and butane

The abilities of three classes of low molecular weight, metal-based, associative compounds to thicken high pressure ethane, propane or butane have been assessed with a close clearance falling ball viscometer. Tributyltin fluoride (TBTF) does not require a heating/cooling cycle to attain dissolution, and at a concentration of 1wt% in ethane, propane or butane yields 70–100-fold viscosity increases at 25°C. Increasing temperature substantially reduces TBTF’s thickening ability. Although hydroxyaluminum di-2-ethylhexanoate (HAD2EH) is insoluble in ethane, it does dissolve in liquid propane or butane after mixing at ∼100°C and cooling to temperatures as low as 40°C. HAD2EH induces small viscosity increases in propane, but is a very effective butane thickener. Increasing temperature causes a relatively small decrease in HAD2EH’s thickening performance. Combining a phosphate ester and a crosslinker in ethane, propane or butane yields a translucent liquid with viscosity increases that are significantly less than those attained with TBTF or HAD2EH.

Crystal Structure of Penicillin-Binding Protein 3 (PBP3) from Escherichia coli

In Escherichia coli, penicillin-binding protein 3 (PBP3), also known as FtsI, is a central component of the divisome, catalyzing cross-linking of the cell wall peptidoglycan during cell division. PBP3 is mainly periplasmic, with a 23 residues cytoplasmic tail and a single transmembrane helix. We have solved the crystal structure of a soluble form of PBP3 (PBP357–577) at 2.5 Å revealing the two modules of high molecular weight class B PBPs, a carboxy terminal module exhibiting transpeptidase activity and an amino terminal module of unknown function. To gain additional insight, the PBP3 Val88-Ser165 subdomain (PBP388–165), for which the electron density is poorly defined in the PBP3 crystal, was produced and its structure solved by SAD phasing at 2.1 Å. The structure shows a three dimensional domain swapping with a β-strand of one molecule inserted between two strands of the paired molecule, suggesting a possible role in PBP357–577 dimerization.

Mucin-based stationary phases as tool for the characterization of drug–mucus interaction

Mucin glycoproteins belong to a class of high molecular weight, heavy glycosylated, proteins that together with water, salts and lipids constitute mucous secretions. Particular disease states (e.g. obstructive chronic bronchitis and ovarian tumor) are known to modify the composition and the thickness of those barriers. Therefore, it is important to address whether the absorption of potential drug candidates to be administered is influenced by the presence of interaction with this class of proteins. Typically, the methods adopted to characterize drug–protein interaction are dialysis, ultrafiltration and gel filtration. Besides these, bio-affinity chromatographic methods have demonstrated to be valuable tools offering the advantageous characteristics such as simplicity, efficiency, high-throughput capability and robustness. The present contribution reports on the synthesis and analytical characterization of a new chromatographic stationary phase based on covalently immobilized mucin and explores the use of LC-UV affinity zonal chromatography as a tool to screen drugs for their affinity to mucin. A series of different binding chemistries for the covalent linkage of mucin to silica-based supports as well as distinct immobilization protocols (static and dynamic) have been evaluated in order to optimize surface coverage. Resultant stationary phases have been characterized chromatographically by studying the effect of mobile phase and analyte structure on the distribution and retention of test compounds. As conclusive study, we report the evaluation of the retention characteristics of 41 drug-like compounds (having heterogeneous chemical properties) for their interaction with this novel stationary phase.