Energetics of the interactions of human serum albumin with cationic surfactant

The heat capacity changes for interaction of human serum albumin (HSA) and a cationic surfactant—cetylpyridinium chloride (CPC), were studied at conditions close to physiological (50 mM HEPES or phosphate buffer, pH 7.4 and 160 mM NaCl) carrying out isothermal calorimetric titrations (ITC) at various temperatures (20-40 °C). ITC measurements indicated that the small endothermic changes associated with CPC demicellization were temperature independent at these conditions. Surprisingly, important enthalpy changes associated with binding of CPC to HSA were exothermic and temperature independent at lower concentrations (below 0.022 mM) of CPC and endothermic and temperature dependent at higher concentrations of CPC. The values of heat capacity changes were obtained for each studied concentration of CPC from the plot of enthalpy changes vs temperature. The obtained results demonstrate the temperature independence of heat capacity changes at entire range of studied CPC concentrations. Both enthalpograms and heat capacity curves indicate the two-step mechanism of HSA folding changes due to its interactions with CPC. The first step corresponds to transition from native state to partially unfolded state and the second to unfolding and to the loss of tertiary structure. The analysis of the results indicates that predominant cooperative unfolding occurs at CPC/HSA molar ratio region between 25 and 30. Such information could not be extracted from thermograms and describes the role of heat capacity as a major thermodynamic quantity giving insight on physical, mechanistic and even atomic-level into how HSA may unfold and interact with CPC. The effect of CPC binding on HSA intrinsic fluorescence, UV-Vis and CD spectra were also examined. Hence, the analysis of spectral data confirms the ITC results about the biphasic mechanism of HSA folding changes induced by CPC. The CD measurement also represents the conservation of considerable secondary structure of HSA due to interaction with CPC.     

Proexosite-1-dependent recognition and activation of prothrombin by taipan venom

An activator complex from the venom of Oxyuranus scutellatus scutellatus (taipan venom) is known to rapidly activate prothrombin to thrombin. To determine whether, similar to prothrombinase, taipan venom utilizes proexosite-1 on prothrombin for a productive complex assembly, the activation of proexosite-1 mutants of prethrombin-1 by the partially purified venom was studied. It was discovered that basic residues of this site (Arg(35), Lys(36), Arg(67), Lys(70), Arg(73), Arg(75), and Arg(77)) are also crucial for recognition and rapid activation of the substrate by taipan venom. This was evidenced by the observation that the K(m) and k(cat) values for the activation of the charge reversal mutants of prethrombin-1 (in particular K36E, R67E, and K70E) were markedly impaired. Competitive kinetic studies with the Tyr(63)-sulfated hirudin(54-65) peptide revealed that although the peptide inhibits the activation of the wild type zymogen by taipan venom with a K(D) of approximately 2 microm, it is ineffective in inhibiting the activation of mutant zymogens (K(D) > 4-30 microm). Interestingly, an approximately 50-kDa activator, isolated from the taipan venom complex, catalyzed the activation of prothrombin in a factor Va-dependent manner and exhibited identical activation kinetics toward the substrate in the presence of the hirudin peptide. These results suggest that, similar to prothrombinase, proexosite-1 is a cofactor-dependent recognition site for taipan venom.     

Modulation of the oviductal environment by gametes

The notion of a gamete recognition system that alerts females to the presence of gametes in their reproductive tract profoundly influences our understanding of the physiology of events leading to conception and the bearing of offspring. Here, we show that the female responds to gametes within her tract by modulating the environment in which pregnancy is initially established. We found distinct alterations in oviductal gene expression as a result of sperm and oocyte arrival in the oviduct, which led directly to distinct alterations to the composition of oviductal fluid in vivo. This suggests that either gamete activates a cell-type-specific signal transduction pathway within the oviduct. This gamete recognition system presents a mechanism for immediate and local control of the oviductal microenvironment in which sperm transport, sperm binding and release, capacitation, transport of oocytes, fertilization, and early cleavage-stage embryonic development occur. This may explain the mechanisms involved in postcopulatory sexual selection, where there is evidence suggesting that the female reproductive tract can bias spermatozoa from different males in the favour of the more biologically attractive male. In addition, the presence of a gamete recognition system explains the oviduct's ability to tolerate spermatozoa while remaining intolerant to pathogens.     

Design,synthesis and anticholinesterase activity of a novel series of 1-benzyl-4-((6-alkoxy-3-oxobenzofuran-2(3H)-ylidene) methyl) pyridinium derivatives

A novel series of benzofuranone-ylidene-methyl benzylpyridinium derivatives (6a–u) were synthesized as acetylcholinesterase inhibitors. The anticholinesterase activity of synthesized compounds was measured using colorimetric Ellman’s method. It was revealed that some synthesized compounds exhibited high anticholinesterase activity, among them compound 6b was the most active compound (IC₅₀ = 10 ± 6.87 nM).     

Is consanguineous marriage religiously encouraged? Islamic and Iranian considerations

Consanguineous marriage has had considerable attention as a causative factor in the prevalence of genetic disorders. Iran, with its majority Muslim population, has a high rate of consanguineous marriage. In Iranian tradition, first cousin marriage is an acceptable and appreciated custom. However, there seems to be no encouragement of consanguineous marriage in the Islamic context; it is merely mentioned as a traditional and common custom. This paper may help medical professionals providing premarital genetic counselling, who are regularly asked about consanguineous marriage, especially in Islamic communities. Increased public awareness via the mass media would seem to be a priority.     

Curved Gratings as Plasmonic Lenses for Linearly Polarised Light

The ability of curved gratings as sectors of concentric circular gratings to couple linearly polarised light into focused surface plasmons is investigated by theory, simulation, and experiment. The experimental and simulation results show that increasing the sector angle of the curved gratings decreases the width of the lateral distribution of surface plasmons resulting in focusing of surface plasmons, which is analogous to the behaviour of classical optical lenses. We also show that two faced curved gratings, with their groove radius mismatched by half of the plasmon wavelength (asymmetric configuration), can couple linearly polarised light into a single focal spot of concentrated surface plasmons with smaller depth of focus and higher intensity in comparison to single curved gratings. The major advantage of these structures is the coupling of linearly polarised light into focused surface plasmons with access to, and control of, the plasmon focal spot, which facilitate their potential applications in sensing, detection, and nonlinear plasmonics.     

Development of Oligoclonal Nanobodies for Targeting the Tumor-Associated Glycoprotein 72 Antigen

The tumor-associated glycoprotein 72 (TAG-72) is a membrane mucin whose over-expression is correlated with advanced tumor stage and increased invasion and metastasis. In this study, we identified a panel of four nanobodies, single variable domains of dromedary heavy-chain antibodies that specifically recognize the TAG-72 antigen. All selected nanobodies were shown to selectively bind to this cancer-related molecule with low-nanomolar affinities and do not cross-react with other antigens, such as MUC1 or HER2. Furthermore, they can detect TAG-72 in concentrations as low as 5 U/ml which is valuable in sensitive detection of this molecule in cancerous patients. Cell ELISA experiments proved their ability for binding to the native target antigen on TAG-72 expressing cells while not showing any reactivity to HT-29 cells, a TAG-72-negative cell line. Using competition studies, we found that each nanobody recognizes a distinct epitope on the TAG-72 antigen that is different from the one recognized by the mouse anti-TAG-72 antibody, CC49. Considering their high specificity, reduced immunogenicity and multi-targeting behavior, these oligoclonal nanobodies represent a promising tool to target TAG-72 over-expressing tumor cells.