Inhibition of horseradish peroxidase activity through conformational change in surfactant solution

Surfactants have a considerable potential for inhibiting horseradish peroxidase (HRP) activity; yet, more research is needed to understand the inhibition mechanism to allow for choosing the suitable surfactant candidate as inhibitor. In this study, three traditional surfactants, sodium dodecyl sulfate (SDS), N-dodecyltrimethyl ammonium bromide (DTAB) and N-dodecyldimethyl (3-sulfopropyl) ammonium hydroxide (SB3-12), that share the same (C₁₂) hydrophobic tail but possess different charged head groups, were taken as model surfactant inhibitors, and the enzymatic activity of HRP was assessed in these surfactant solutions. The activity of HRP was inhibited by both anionic SDS and cationic DTAB at dilute concentration even below their critical micelle concentration (cmc), and the electrostatic interaction of the ionic surfactants with some amino residues of HRP was mainly responsible for the inhibition of activity. HRP in a dilute solution of SB3-12, with the latter's concentration being below its cmc, retained a high level of enzymatic activity; but, at concentrations above the cmc of SB3-12, HRP was inhibited owing to the synergetic interaction of the SB3-12 micelle with HRP. Results from circular dichroism (CD) and intrinsic fluorescence spectroscopic analyses of HRP showed the unfolding of the tertiary structure around HRP's heme active site played a critical role in the inhibition, whereas the changes of HRP in the secondary structure and the tertiary structure near its tryptophan residue (Trp117) induced by these surfactants were minor for the inhibition. Based on the experimental results, a relationship between conformation and activity for HRP was suggested.     

Considerations in the development of an in vitro dissolution condition for lacidipine tablets: in vivo pharmacokinetic evaluation

In this study, a new discriminative dissolution condition for lacidipine tablets was developed by the established in vitro–in vivo relationship. Series of dissolution media of phosphate buffer solution (PBS) covering the pH range of 1–7.2 and pH 6.8 PBS containing different concentrations of sodium dodecyl sulfate (SDS), were prepared and used to investigate the dissolution behavior of lacidipine tablets. There was an obvious difference in the dissolution profiles of the both brands in pH 6.8 PBS medium containing 0.1% SDS. The pharmacokinetic study of the two lacidipine tablets was carried out in the healthy beagle dogs at a single dose of 4?mg. Statistical comparison of the AUC_0–24, C_max, and T_max showed a significant difference in the two brand tablets, coinciding with the dissolution performance with pH 6.8 PBS containing 0.1% SDS. The superiority of the proposed system, pH 6.8 PBS containing 0.1% SDS, could serve as a dissolution medium for lacidipine tablets, and more important it could discriminate the in vivo pharmacokinetic behavior for different brands of products. In summary, in vivo pharmacokinetic evaluation is essential to develop an appropriate in vitro dissolution condition for oral solid dosage forms of poorly soluble drugs.     

Occurrence and molecular identification of anisakid nematodes isolated from Pacific cod (Gadus macrocephalus) caught off Korea

Anisakids nematodes from Pacific cod (Gadus macrocephalus) in Korea were investigated and their molecular identification was conducted, to assess the epidemiological role of Pacific cod in human anisakidosis in Korea. Totally 238 Pacific cod were caught from 5 different areas around Korean peninsula. Fish were dissected and carefully examined for collecting nematodes. PCR-RFLP and the subsequent sequencing were conducted for molecular identification of those nematodes. A high prevalence of infection (193/238, 81.1%) in Pacific cod was observed, and 1694 nematodes were collected. 79.1% (1340/1694) of the nematodes were found freely in the body cavity of Pacific cod, and the rest of them (20.9%, 354/1694) were in the digestive tract or attached to other organs. PCR-RFLP analysis using HinfI and RsaI restriction enzymes revealed 3 different banding patterns corresponding to Anisakis pegreffii, Hysterothylacium aduncum and hybrid genotype (Anisakis simplex × A. pegreffii), respectively. Of 1694 nematodes, 1280 (75.6%) were identified as A. pegreffii and 406 (24.0%) were H. aduncum. A. pegreffii occupied 84.0% (1125/1340) of the nematodes in the body cavity and 40.0% (132/330) of them in the digestive tract, but no nematodes were found in Pacific cod muscles.     

The impact of the protein network on the pasting and cooking properties of dry pasta products

Durum wheat semolina gluten and starch as well as processing conditions determine pasta cooking quality. This study investigated whether, for good organoleptic properties, a permanent protein network needs to be formed during pasta drying or can still be formed during cooking. The cooking quality of 16 spaghetti samples was related to the levels of sodium dodecyl sulphate extractable protein (SDSEP), starch gelatinisation temperatures as well as to the swelling properties of milled dry spaghettis. SDSEP levels in dry and cooked products varied between 31% and 56%, and 12% to 21% of total protein contents, respectively. The highest quality spaghettis had relatively higher levels of SDSEP in the dry product, low starch gelatinisation temperatures and swelling powers, and rigid particles. The lowest quality spaghettis had lower levels of SDSEP and higher gelatinisation temperatures. This work implies that high pasta quality results from an optimal degree of protein polymerisation during drying and/or the subsequent cooking.     

Sodium Dodecyl Sulfate (SDS)-Loaded Nanoporous Polymer as Anti-Biofilm Surface Coating Material

Biofilms cause extensive damage to industrial settings. Thus, it is important to improve the existing techniques and develop new strategies to prevent bacterial biofilm formation. In the present study, we have prepared nanoporous polymer films from a self-assembled 1,2-polybutadiene-b-polydimethylsiloxane (1,2-PB-b-PDMS) block copolymer via chemical cross-linking of the 1,2-PB block followed by quantitative removal of the PDMS block. Sodium dodecyl sulfate (SDS) was loaded into the nanoporous 1,2-PB from aqueous solution. The SDS-loaded nanoporous polymer films were shown to block bacterial attachment in short-term (3 h) and significantly reduce biofilm formation in long-term (1 week) by gram-negative bacterium Escherichia coli. Tuning the thickness or surface morphology of the nanoporous polymer films allowed to extent the anti-biofilm capability.     

Preparation of colloidal silver nanoparticles by chemical reduction method

Colloidal silver nanoparticles were obtained by chemical reduction of silver nitrate in water with sodium borohydride (NaBH₄) in the presence of sodium dodecyl sulfate (SDS) as a stabilizer. The obtained nanoparticles were characterized by their UV-vis absorption spectra and transmission electron micrograph (TEM) images. The UV-vis absorption spectra showed that NaBH₄ served not only as a reducing agent but also as a stabilizer, which protects the aggregation of silver nanoparticles. The TEM images showed that the particles were dispersed better with increasing the NaBH₄ concentration.     

一种新的运动搜索算法

根据序列图像中运动矢量的中心偏置分布特性和矢量间的时空相关性,设计了一种基于连续消除的正方形-菱形搜索策略。在此基础上,融合了搜索起点预测和自适应搜索等技术,提出了一种可预测搜索起点的自适应的基于连续消除的正方形-菱形搜索算法（PA-SEA-SDS）。实验表明,该算法以较小的代价取得了与全搜索算法相当的效果,在搜索次数和精度上均优于菱形和正方形-菱形搜索算法。     

基于Ericsson SDS的IMS客户端开发

Ericsson公司发布的SDS开发环境是一款基于Eclipse平台的、免费的软件,在目前IMS网络尚未完全铺设的条件下,为开发人员提供开发、测试和仿真新业务的平台。它内置服务器、协议栈、IMS核心网,并提供各种模拟器,为我们开发新业务提供极大的便利。主要介绍了采用Ericsson SDS对IMS客户端进行开发与仿真,实现新业务。     

Partial properties of an aspartic protease in bitter gourd (Momordica charantia L.) fruit and its activation by heating

Bitter gourd (BG fruit) is usually heated in hot water to reduce bitterness and improve flavour before being served. Protein extract from BG was analyzed for protease activity by gelatin-gel electrophoresis. The study showed that the proteolytic activity in BG flesh was enhanced by heat-treatment at temperatures ranging from 50 °C to 75 °C. An aspartic protease (AP) was characterized by gel electrophoresis. The optimal AP activity was at pH 7; the pI of the AP was demonstrated to be 4.8; the protein molecular weight of the BG–AP was estimated to be 60 KD by SDS–PAGE. The AP was implicated in the proteolysis of the photosynthetic enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase.