The influence of diet and water on the stable oxygen and hydrogen isotope composition of Chironomidae (Diptera) with paleoecological implications

Stable oxygen and hydrogen isotope analyses of fossil aquatic organisms, such as the chitinous head capsules of chironomid larvae (Chironomidae: Diptera), are promising proxies for inferring paleoecological conditions. In order for analyses of stable oxygen (δ¹⁸O) and hydrogen isotope ratios (δ²H) of fossil chironomid head capsules to be used effectively in paleoecological research, it is necessary to understand the factors controlling their stable oxygen and hydrogen composition. We cultured chironomid larvae in two isotopically distinct waters under controlled, replicated laboratory conditions. Chironomid larvae were fed on identical diets, to examine the degree to which water and diet influence the δ¹⁸O and δ²H of these organisms. We used a two-end member mixing model to determine the proportional contributions of oxygen and hydrogen from water to the oxygen and hydrogen of chironomid larvae. Our experiment demonstrated that 69.0 ± 0.4% of oxygen and 30.8 ± 2.6% of hydrogen in chironomid larvae are derived from habitat water. Our results show that oxygen isotopes from chironomid remains can better constrain past habitat water isotopic changes compared to hydrogen, due to 69% of the chironomid oxygen being influenced by habitat water. Our data add to a small but growing suite of comparative data on the sources of oxygen and hydrogen in animal tissues, and provide the first such analyses from aquatic insects.     

Modulation and Optimization of Drug Release from Uncoated Low Density Porous Carrier Based Delivery System

The purpose of this research work was to explore an application of uncoated porous drug carrier prepared by single-step drug adsorption for a delivery system based on integration of floating and pulsatile principles intended for chronotherapy. This objective was achieved by utilizing 3² factorial design, solvent volume (X ₁) and drug amount (X ₂) as selected variables, for drug adsorption using solvents, methanol, and dichloromethane (DCM), of varying polarity. Nitrogen adsorption (N₂), scanning electron microscopy of cross-sections, and atomic force microscopy were done to study adsorption patterns and their effect on release pattern. Drug release study was customized by performing for 6 h in acidic environment to mimic gastroretention followed by basic environment akin to transit phase. Correlation between porous data from mercury and N₂ adsorption was probably studied for the first time. Observed regression analysis values for pore volume, surface area, and drug release indicated the influence of selected variables. Total release range in acidic medium was 12.77–24.57% for methanol, 8.79–15.26% for DCM, and final release of 69.45–92.23% for methanol, and 60.16–99.99% for DCM influenced by varying internal geometries was observed. Present form of drug delivery system devoid of any additives/excipients influencing drug release shows distinct behavior from other approaches/technologies in chronotherapy by (a) observing desired low drug release (8%) in acidic medium, (b) overcoming the limitations of process variables caused by multiple formulation steps and different characteristic polymers, (c) reducing time consumption due to single step process, and (d) extending as controlled/extended release.     

Coordinated cations in dipicolinato complexes of divalent metal ions

Several salts of alkali, alkaline earth metal and organic ammonium cations of a complex anion [ML₂]²⁻ {Where L = dipicolinato dianion, M = copper(II), nickel(II) and zinc(II)} are prepared. The coordination effect of [ML₂]²⁻ with the cations such as sodium, potassium, calcium, magnesium, and organic cations namely diammonium cation of 1,5-pentanediamine, diammonium cation of 1,8-octyldiamine, mono ammonium cation of 4-aminobenzylamine are studied by determining their X-ray crystal structures. Depending on the nature of cations, four different types of structures are obtained. When calcium is the cation a polymeric structure with calcium ions bridging the [ML₂]²⁻ is observed. The salts having sodium and potassium cations form polymeric chain like structures by oxo and aqua bridges. In the case of magnesium, the hydrated form of magnesium cations coordinates to [ML₂]²⁻. The organic ammonium salts of [ML₂]²⁻ have the structural features of conventional ionic complexes. These salts easily exchange cations. The organic ammonium salts of [ML₂]²⁻ decomposes to give the corresponding metal oxides at relatively low temperature range 300-450 °C.     

LpxA: A natural nanotube

UDP‐N‐acetylglucosamine 3‐O‐acyltransferase is a protein with a left‐handed parallel β‐helix, which is a natural nanotube. They are associated with unusual high stability. To identify the reason behind the structural stability of β‐helical nanotubular structure, we have performed a total of 4 μs molecular dynamics simulations of the protein in implicit solvent at four different temperatures and monitored the unfolding pathway. The correlation in movement between different regions of the nanotubular structure has been identified from the dynamical cross‐correlation map and contribution of some specific residues towards unfolding transition has been identified by principal component analysis. Difference in stability of the three loop regions has also been characterized. Construction of the unfolding conformational energy landscape identifies the probable intermediates that can appear in the unfolding pathway of the protein. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 845–853, 2010.     

Michael Addition of Pyrimidine with Disaccharide Acrylates Catalyzed in Organic Medium with Lipase M from Mucor javanicus

The Michael addition of fluorouracil (0.01 mol), uracil (0.01 mol), thymine (0.01 mol) to disaccharide acrylates (0.03 mol) was carried out in pyridine (20 ml) at 50°C for 72 h with lipase M from Mucor javanicus (200 mg). Six new pyrimidine derivatives containing a branched sugar were obtained in yields from 56 to 75%.     

Effect of organic solvents on the conformation and interaction of catalase and anticatalase antibodies

Effect of six organic solvents—methanol, ethanol, propanol, dimethyl sulphoxide (DMSO), N,N-dimethyl formamide (DMF), and glycerol on the conformation and interaction of catalase and anticatalase antibodies were studied with the aim of identifying the solvents in which antigen–antibody interactions are strong. The antigen binding activity of the antibodies in the various organic solvents increased in the following order: ethanol < methanol < no organic solvent < propanol < DMSO < DMF < glycerol. The structure of both the antibody and the antigen molecule was affected significantly in 40% concentration of the organic solvents used in this study. Catalase activity was inhibited in DMSO. However, the enzyme was activated in DMF upto about 50% of its concentration.     

Olfactory mucosa-expressed organic anion transporter, Oat6, manifests high affinity interactions with odorant organic anions

We have characterized the expression of organic anion transporter 6, Oat6 (slc22a20), in olfactory mucosa, as well as its interaction with several odorant organic anions. In situ hybridization reveals diffuse Oat6 expression throughout olfactory epithelium, yet olfactory neurons laser-capture microdissected from either the main olfactory epithelium (MOE) or the vomeronasal organ (VNO) did not express Oat6 mRNA. These data suggest that Oat6 is expressed in non-neuronal cells of olfactory tissue, such as epithelial and/or other supporting cells. We next investigated interaction of Oat6 with several small organic anions that have previously been identified as odortype components in mouse urine. We find that each of these compounds, propionate, 2- and 3-methylbutyrate, benzoate, heptanoate, and 2-ethylhexanoate, inhibits Oat6-mediated uptake of a labeled tracer, estrone sulfate, consistent with their being Oat6 substrates. Previously, we noted defects in the renal elimination of odortype and odortype-like molecules in Oat1 knockout mice. The finding that such molecules interact with Oat6 raises the possibility that odorants secreted into the urine through one OAT-mediated mechanism (Eraly et al., JBC 2006) are transported through the olfactory mucosa through another OAT-mediated mechanism. Oat6 might play a direct or indirect role in olfaction, such as modulation of the availability of odorant organic anions at the mucosal surface for presentation to olfactory neurons or facilitation of delivery to a distal site of chemosensation, among other possibilities that we discuss.     

Triple helical structure and stabilization of collagen-like molecules with 4(R)-hydroxyproline in the Xaa position

In this study, we examine the relationships between the structure and stability of five related collagen-like molecules that have hydroxyproline residues occupying positions not observed in vertebrate collagen. Two of the molecules contain valine or threonine and form stable triple helices in water. Three of the molecules contain allo-threonine (an enantiomer of threonine), serine, or alanine, and are not stable. Using molecular dynamics simulation methods, we examine possible explanations for the stability difference, including considering the possibility that differences in solvent shielding of the essential interchain hydrogen bonds may result in differences in stability. By comparing the structures of threonine- and allo-threonine-containing molecules in six polar and nonpolar solvation conditions, we find that solvent shielding is not an adequate explanation for the stability difference. A closer examination of the peptides shows that the structures of the unstable molecules are looser, having weaker intermolecular hydrogen bonds. The weakened hydrogen bonds result from extended Yaa residue Psi-angles that prevent optimal geometry. The Phi-Psi-maps of the relevant residues suggest that each residue's most favorable Psi-angle determines the corresponding collagen-like molecule's stability. Additionally, we propose that these molecules illustrate a more general feature of triple-helical structures: interchain hydrogen bonds are always longer and weaker than ideal, so they are sensitive to relatively small changes in molecular structure. This sensitivity to small changes may explain why large stability differences often result from seemingly small changes in residue sequence.     

Immunophysical properties and prediction of activities for vaccinia virus complement control protein and smallpox inhibitor of complement enzymes using molecular dynamics and electrostatics

We present immunophysical modeling for VCP, SPICE, and three mutants using MD simulations and Poisson-Boltzmann-type electrostatic calculations. VCP and SPICE are homologous viral proteins that control the complement system by imitating, structurally and functionally, natural regulators of complement activation. VCP and SPICE consist of four CCP modules connected with short flexible loops. MD simulations demonstrate that the rather complex modules of VCP/SPICE and their mutants exhibit a high degree of intermodular spatial mobility, which is affected by surface mutations. Electrostatic calculations using snapshots from the MD trajectories demonstrate variable spatial distribution of the electrostatic potentials, which suggests dynamic binding properties. We use covariance analysis to identify correlated modular oscillations. We also use electrostatic similarity indices to cluster proteins with common electrostatic properties. Our results are compared with experimental data to form correlations between the overall positive electrostatic potential of VCP/SPICE with binding and activity. We show how these correlations can be used to predict binding and activity properties. This work is expected to be useful for understanding the function of native CCP-containing regulators of complement activation and receptors and for the design of antiviral therapeutics and complement inhibitors.     

Scale-up of a pan-coating process

The purpose of this work was to develop a practical scale-up model for a solvent-based pan-coating process. Practical scale-up rules to determine the key parameters (pan load, pan speed, spray rate, air flow) required to control the process are proposed. The proposed scale-up rules are based on a macroscopic evaluation of the coating process. Implementation of these rules does not require complex experimentation or prediction of model parameters. The proposed scale-up rules were tested by conducting coating scale-up and scale-down experiments on 24-inch and 52-inch Vector Hi-coaters. The data demonstrate that using these rules led to similar cumulative drug release profiles (f2≫50; and P Analysis of Variance [P _ANOVA]≫0.05 for cumulative percentage of drug released after 12 hours [Cum 12] from tablets made at 24- and 52-inch scales. Membrane characteristics such as opacity and roughness were also similar across the 2 scales. The effects of the key process variables on coat weight uniformity and membrane characteristics were also studied. Pan speed was found to be the most significant factor related to coating uniformity. Spray droplet size was found to affect the membrane roughness significantly, whereas opacity was affected by the drying capacity.