Crinumin,a chymotrypsin-like but glycosylated serine protease from Crinum asiaticum: Purification and physicochemical characterisation

Plant latex could be a potential source of novel proteases usable in the food and feed industries because of broad substrate specificity with high stability in extreme conditions. Crinumin, a glycosylated serine protease with chymotrypsin-like activity was purified from the latex of Crinumasiaticum using cation-exchange column chromatography. Crinumin shows activity over a wide range of pH (4.5–11.5 and optimum at 8.5), temperature (75 °C and optimum at 70 °C) and is also functional against chaotrophs, organic solvents, and detergents, even after prolonged exposure. The molecular mass (67.7 kDa), extinction coefficient (17.7), isoelectric point (6.9), and numbers of tryptophan (13), tyrosine (24) and cysteine (15 with 7 disulphide bridges) residues were estimated. K_m of the enzyme was 31.7 μM with casein and 5 × 10⁴ μM with N-succinyl-l-phenylalanine-p-nitroanilide. Easy availability of the aqueous latex, simple purification procedure, high yield (33%), stability and activity in adverse conditions makes it applicable for the pharmaceutical and food industries.     

Neriifolin S, a dimeric serine protease from Euphorbia neriifolia Linn.: Purification and biochemical characterisation

A dimeric serine protease Neriifolin S of molecular mass 94 kDa with milk clotting activity has been purified from the latex of Euphorbia neriifolia by anion exchange and size-exclusion chromatography. It hydrolyses peptidyl substrates l-Ala-pNA with highest affinity (K_m of 0.195 mM) and physiological efficiency (K_cat/K_m of 144.5 mM s). Enzyme belongs to the class of neutral proteases with pI value of 6.8, optimal proteolytic activity displayed at pH 9.5 and temperature 45 °C. Its proteolytic activity is strongly stimulated in the presence of Ca⁺² ions and exclusively inhibited by serine protease inhibitors. Enzyme is fairly stable toward chemical denaturants, pH and temperature. The apparent T_m, was found to be 65 °C. Thermal inactivation follow first order kinetics with activation energy (Ea), activation enthalpy (ΔH∗), free energy change (ΔG∗) and entropy (ΔS∗) of 27.54 kJ mol⁻¹, 24.89 kJ mol⁻¹, −82.34 kJ mol⁻¹ and 337.20 J mol⁻¹ K⁻¹.     

EGTA滴定法测定稀土合金中稀土总量

通过对稀土中干扰元素的掩蔽 ,用EGTA对稀土总量进行快速测定     

EGTA滴定法快速测定碳酸钙中CaC03

利用CaCO3易溶解于稀醋酸而其它钙盐不被溶解的原理，用稀醋酸溶解试样，过滤与其它不被溶解的钙盐及物质分离。滤液在三乙醇胺掩蔽剂存在下，加入氢氧化钾调节溶液PH≥12．5，以钙磺绿素一百里香酚酞为指示剂，用EGTA标准溶液滴定至绿色荧光消失变紫红色为终点，借此测定CaCO3的百分含量。     

EGTA荧光滴定法快速测定硅铝钙钡合金中的钙钡元素

EGTA荧光滴定法快速测定钙钡,因钙钡两元素的化学性质近似,相互干扰不能进行钙钡的联合测定。本文用稀硫酸沉淀钡为硫酸钡,借此消除钡对钙滴定的影响,实现了EGTA荧光滴定法快速测定钙钡。方法操作简便、快速,结果准确。     

转炉渣中CaO和CaF2的分析

利用氧化钙易溶解于稀醋酸,而氟化钙不溶解于稀醋酸的特性.试样以稀醋酸处理,用滤纸过滤不溶解物残渣,滤液加氢氧化钾溶液调节pH≥12.5,用EGTA滴定法测定CaO含量.过滤的不溶解物残渣在铂金坩埚中灰化、灼烧,加含有硼酸钠的混合熔剂,于950℃左右熔融、酸化浸取定容、分液后,加氢氧化钾溶液调节pH≥12.5,用EGTA滴定法测定CaF2含量.     

M-line protein: Presence of two non-equivalent high molecular weight components

M-line enriched protein preparations were prepared from glycerated rabbit muscle myofibrils by means of three alternate procedures and analysed with SDS-polyacrylamide gel electrophoresis. A doublet corresponding to polypeptides with molecular weights of 193,000 and 182,000 was obtained in a ratio of2:3, respectively. The two bands are evident in SDS-gels of purified myofibrils, indicating that the proteins represent intrinsic M-line structural peptides. Transmission electron micrographs of the extracted myofibrils confirmed the effectiveness of the extraction procedures for removing M-line proteins. The possible significance of the M-line proteins to meat science is discussed.     

Stimuli-triggered structural engineering of synthetic and biological polymeric assemblies

Response to external stimuli is a fundamental and intrinsic behavior of living systems. There has been increasing interest for designing and constructing responsive polymeric superstructures by self-assembly. Stimuli-induced self-assembly and post-assembly triggering strategies provide an alternative approach for the manipulation of self-assembled architectures of either biological or synthetic polymeric materials. Stimuli-induced structural transformations may produce ensembles with new topologies or materials with exceptionally complex features inaccessible via conventional self-assembly processes. This is in contrast to materials that simply undergo stimuli-induced degradation, or disassembly processes. Since a variety of cellular processes depend on responses to environmental stimuli that lead to more complexity and increased function, and are related to structural transitions over the nano- to microscale, insights into stimuli-triggered morphogenesis can further deepen our understanding of cellular behaviors. Indeed, an understanding of these processes will likely inspire scientists to develop materials with advanced and tailored architectures for biosensing, diagnosis and therapy as well as other biomedical applications. Herein, we highlight state-of-the-art achievements in the stimuli-triggered structural manipulation of polymer assemblies. Furthermore, future developments in this nascent and growing field are briefly discussed.     

Physiological adaptations in early-lactation cows result in differential responses to calcium perturbation relative to nonlactating,nonpregnant cows

The peripartal cow experiences a rapid change in calcium metabolism at the onset of lactation. Research has focused on understanding how mammary-derived factors, such as serotonin (5HT) and parathyroid hormone like hormone (PTHLH), aid in coordinating these calcemic adaptations to lactation. Therefore, the aim of our study was to determine how induced subclinical hypocalcemia influences physiological responses, specifically the 5HT-PTHLH-Ca axis, in lactating and nonlactating dairy cows to elucidate the potential contribution of the mammary gland. Twelve nonlactating, nonpregnant (NL) multiparous Holstein cows and 12 early-lactation (EL) multiparous Holstein cows received either (1) a continuous 24-h intravenous solution of 0.9% NaCl or (2) 5% ethylene glycol tetraacetic acid (EGTA) solution in 0.9% NaCl (n = 6 EL, n = 6 NL per treatment) with the aim of maintaining blood ionized calcium (iCa) less than 1.0 mM. Mammary gland biopsies were taken immediately after and 48 h after termination of infusion. Blood was sampled hourly during infusion and 4, 8, 12, 24, 48, and 72 h after termination of infusion. Infusion of EGTA successfully decreased blood iCa concentrations. However, EL EGTA-infused cows required increased rates of EGTA infusion to maintain iCa below 1.0 mM. Circulating and mammary serotonin concentrations were increased in EL relative to NL cows, with no difference as a result of EGTA infusion. Mammary PTHLH expression was increased in EL cows, with highest expression observed in EL EGTA-infused cows. Collectively, these data demonstrate the robust adaptations EL cows have to maintain Ca homeostasis and the supporting roles 5HT and PTHLH may play.