Stabilizing mutations and calcium-dependent stability of subtilisin

Stability is a property of subtilisin which has proven particularly amenable to enhancement via random mutagenesis and screening, yet the effects of most stabilizing mutations are not understood in structural and energetic detail. This paper seeks to explain the longstanding observation that stabilizing mutations are usually calcium-dependent in their stabilizing effect, irrespective of their proximity to the calcium binding sites. Stabilizing mutations in subtilisin fall into one of three classes. The largest class of mutations stabilize only in the presence of excess calcium. A smaller number of mutations stabilize independently of [calcium], and a few mutations stabilize only in the presence of chelating agents, such as EDTA. This study compares the effects of mutations from each class when introduced into subtilisin BPN' and two calcium-free versions of subtilisin. The calcium-dependent effects of mutations can be explained by considering subtilisin to be in conformational equilibrium between two structurally similar but energetically distinct states: N and N*. The equilibrium from the N* to the N state can be altered either by calcium binding to site A or by mutation. Mutations which stabilize only in the presence of calcium stabilize the N state relative to N*. Mutations which stabilize only in the presence of chelants stabilize the N* state relative to N. As a byproduct of this analysis, we have developed a hyperstable variant of subtilisin whose inactivation at high temperature in the presence of EDTA is 10(5) times slower than wild-type subtilisin.     

Regulation of insulin sensitivity by adipose tissue-derived hormones and inflammatory cytokines

PURPOSE OF REVIEW: The aim of this review is to assess the role of adipose tissue-derived hormones and inflammatory cytokines in the pathogenesis of obesity-linked type II diabetes, with a special focus on articles published between December 2002 and December 2003. RECENT FINDINGS: Insulin resistance is widely recognized as a fundamental defect seen in obesity and type II diabetes. Although the molecular mechanisms triggering the development of insulin resistance remain elusive, recent studies have suggested that adipose tissue and adipose tissue-derived hormones and inflammatory cytokines play essential roles in the overall insulin sensitivity in vivo. Dysfunctions of adipose tissue can lead to systemic insulin resistance. SUMMARY: Understanding the regulation of the metabolic and secretory functions of adipose tissue, as well as its subsequent impact on overall insulin sensitivity, is becoming increasingly important given the therapeutic potential of targeting the root causes of insulin resistance in the treatment of type 2 diabetes and its associated complications, such as cardiovascular and cerebrovascular diseases.     

A one pot synthesis of mono- and di-lactosyl sphingosines

The importance of analogues of lactosyl ceramides as basic structures of many natural glycosphingolipids provided a rationale for developing an efficient synthetic route to these compounds. We report herein a novel approach to synthesize several members of this family. Glycosylation of N-diphenylmethylene-spingosine, which exists in an imine–oxazolidine tautomeric mixture, with acetobromolactose under a modified Koenigs-Knorr condition yielded lactosyl -(1 1) sphingosine, lactosyl -(1 3) sphingosine and dilactosyl sphingosine in good yields. A similar glycosylation could be applicable to the synthesis of other glycosphingolipids.     

Effects of sex hormones and their balance on the proliferation of rat vascular endothelial cells

OBJECTIVE: To investigate the adjustment of estrogen, progesterone and testosterone on the proliferation of female and male rat vascular endothelial cells (VECs) separately. METHODS: Rat lung VECs were cultured according to the block explanting method. MTT assay was used to measure the proliferation of VECs. RESULTS: 17beta-Estradiol (E(2)) at 3 x 10(-8) and 3 x 10(-7) M accelerated the proliferation of female rat VECs (p < 0.01). E(2) at 3 x 10(-9), 3 x 10(-8) and 3 x 10(-7) M accelerated the proliferation of male rat VECs (p < 0.05). Tamoxifen, the estrogen receptor antagonist, could block the effect of estrogen on the proliferation of VECs. Testosterone at 3 x 10(-8) and 3 x 10(-7) M significantly increased the proliferation of male rat VECs (p < 0.05), but had no effect on female rat VECs. Progesterone at 10(-9) and 10(-8) M had no effect on female rat VECs alone. When the ratio of E(2) to progesterone was 3/10, the proliferation of female rat VECs was accelerated (p < 0.05). When the ratio of E(2) to testosterone was 1/1, the proliferation of female rat VECs was also hastened (p < 0.05). However, when the ratio was reduced to 1/100, the hastening effect disappeared. CONCLUSION: Estrogen can speed up the proliferation of female and male rat VECs, while progesterone has no effect on female rat VECs alone. The balance of the ratio of E(2) to testosterone, E(2) to progesterone may play an important role in the proliferation of female rat VECs.     

Ⅱ型肺泡上皮细胞与特发性肺纤维化的关系研究进展

特发性肺纤维化（IPF）是一种严重影响肺通气与换气功能的下呼吸道慢性疾病,其发病机理目前尚不明确,表现为异常的间质炎症和纤维化,以及肺泡结构的破坏。而Ⅱ型肺泡上皮细胞（ATⅡ）作为维持肺结构和功能的关键细胞,在肺部纤维化的发生和发展中极其重要。在IPF中,各种原因所致的ATⅡ的受损和衰老凋亡,可能是纤维化发生的是始动因素。而在这之后,关于临时基质的形成、成纤维细胞的聚集、激活以及间质-上皮转化的过程,异常的ATⅡ也参与其中,并发挥着重要的作用。     

Modelling diapause in mosquito population growth

Journal of Mathematical Biology - Diapause, a period of arrested development caused by adverse environmental conditions, serves as a key survival mechanism for insects and other invertebrate...     

Calorimetric Study of Nonspecific Interaction Between Lead Ions and Bovine Serum Albumin

The nonspecific interaction between lead ions and bovine serum albumin (BSA) was studied by the calorimetric technique. According to thermodynamic parameters calculated from titration curves, it can be seen that the increase of intermolecular bond energies and decrease of disorder in the system were accompanied by a binding process. This kind of binding is the reaction “driven by enthalpy.” Furthermore, the denatured BSA has more binding sites and more changes in enthalpy and entropy than the native BSA because the unfolded chain of denatured BSA could adapt itself to the binding reaction with lead ions more easily.     

Polymorphisms of Chicken TLR3 and 7 in Different Breeds

Toll-like receptors (TLRs) mediate immune responses via the recognition of pathogen-associated molecular patterns (PAMPs), thus playing important roles in host defense. Among the chicken (Ch) TLR family, ChTLR3 and 7 have been shown to recognize viral RNA. In our earlier studies, we have reported polymorphisms of TLR1, 2, 4, 5, 15 and 21. In the present study, we amplified TLR3 and 7 genes from different chicken breeds and analyzed their sequences. We identified 7 amino acid polymorphism sites in ChTLR3 with 6 outer part sites and 1 inner part site, and 4 amino acid polymorphism sites in ChTLR7 with 3 outer part sites and 1 inner part site. These results demonstrate that ChTLR genes are polymorphic among different chicken breeds, suggesting a varied resistance across numerous chicken breeds. This information might help improve chicken health by breeding and vaccination.