EFFECTS OF CALDESMON, CALPONIN, AND TROPOMYOSIN ON THE MG^(2+)-ATPase ACTIVITIES OF SMOOTH MUSCLE MYOSIN

Objective To test whether in the absence of actin, actin-binding proteins such as caldesmon, calponin, and tropomyosin interact with the myosin of unphosphorylation, Ca 2+ -dependent phosphorylation (CDP), and Ca 2+ -independent phosphorylati-on (CIP) and stimulate myosin Mg 2+ -ATPase activities. Methods Mg 2+ -ATPase activities were measured to evaluate the effects of caldesmon, calponin, and tropomyosin on the myosin in unphosphorylation, CDP by myosin light chain kinase (MLCK), and CIP by MLCK. Results (1) At different incubation-time, i.e., 5, 10, 20, 40, and 60 minutes, the highest Mg 2+ -ATPase activity was ob-served when myosin was in the state of CDP, the medium was CIP of myosin, and the lowest was the unphosphorylated myosin. (2) In the absence of caldesmon, calponin, and tropomyosin, the Mg 2+ -ATPase activities from high to low were in the following order: CDP, CIP, and unphosphorylated myosin. However, in the presence of caldesmon, calponin, and tropo-myosin, the order of relative value of Mg 2+ -ATPase activities from high to low was unphosphorylated, CIP, and CDP of myosin respectively compared to the corresponding controls. Conclusions The results propose that caldesmon, calponin, and tropomyosin are capable of stimulating Mg 2+ -ATPase activity of smooth muscle myosin in Ca 2+ -independent manner, since Ca 2+ is not obligating for the stimulating effects of the three proteins. The common characteristic of the three proteins is that when myosin activities are low, their activations are relatively strong and this property might be involved in smooth muscle tension keeping.

基于分子对接技术研究铁线透骨草提取物通过Ca2+/NFATc1信号通路对骨质疏松性骨折大鼠骨折愈合的影响

目的基于分子对接技术研究铁线透骨草提取物通过Ca2+/活化T细胞核因子(NFAT)c1信号通路对骨质疏松性骨折大鼠骨折愈合的影响。方法40只SPF级SD雌性大鼠随机分为对照组、模型组、低剂量组、高剂量组各10只,除对照组外均构建骨质疏松大鼠模型,对所有大鼠行骨折造模,造模结束后低、高剂量组分别给予不同剂量铁线透骨草提取液灌胃(100、400 mg/kg),对照组及模型组均给予生理盐水溶液灌胃(5 ml/kg)。给药结束后,观察大鼠骨折端愈合情况并进行评分;检测骨密度水平;苏木素-伊红(HE)染色观察骨痂组织病理结构;采用酶联免疫吸附试验试剂盒检测血清Ca、白细胞介素(IL)-6、肿瘤坏死因子(TNF)-α水平;取骨折部位肌肉组织采用Western印迹检测磷酸化(p)-NFATc1蛋白表达。对铁线透骨草提取物中所含活性成分收集与筛选,并对有效成分-靶点进行分子对接。结果相较于对照组,模型组骨质疏松骨折愈合评分、骨密度明显降低,Ca、TNF-α、IL-6水平及p-NFATc1蛋白表达均明显升高(P<0.05);而经不同剂量铁线透骨草提取物给药后,骨折愈合评分、骨密度均明显提高,Ca、TNF-α、IL-6水平及p-NFATc1蛋白表达明显降低(P<0.05)。铁线透骨草提取物中主要活性成分为谷甾醇(sitosterol)、山奈酚(kaempferol)、槲皮素(quercetin),分子对接结果显示与Ca2+靶点对接较好的成分是sitosterol,结合能为-6.24,与NFATc1靶点对接较好的成分是sitosterol,结合能为-6.81。结论铁线透骨草提取物能够显著改善骨质疏松大鼠骨折的愈合情况,并且可能通过调节Ca2+/NFATc1通路,进一步影响炎症反应。

焙烧脱碳对含钒石煤相变及浮选行为的影响

湖北某高钙云母型含钒石煤中矿物被碳质深度浸染,浮选前需要焙烧脱碳。通过热重-差示扫描量热(TG-DSC)、傅里叶红外光谱(FTIR)、X射线衍射(XRD)等分析测试手段对原矿及不同温度焙烧脱碳样进行了表征分析,探讨了不同温度脱碳对浮选行为的影响。结果表明,该含钒石煤随着焙烧温度的升高,依次发生黄铁矿氧化、碳质的燃烧、方解石的分解等反应。600~700℃,碳质和黄铁矿基本消失,云母八面体结构未被破坏,方解石部分分解,固硫后剩余的CaO使浮选矿浆pH值升高,Ca^(2+)浓度增大。浮选试验结果表明,随焙烧温度的提高,碳质逐渐脱除,矿物表面性质差异扩大,脱碳样的浮选效果比原矿有明显改善。650℃脱碳样浮选,由于Ca^(2+)的活化作用,石英被油酸钠捕收,可得产率为21.10%,V_2O_5品位为0.36%的尾矿产品,钒损失率仅为10.05%,精矿的V_2O_5品位为0.95%。700℃脱碳时,矿浆过高的pH值和Ca^(2+)含量使微细颗粒发生无选择性聚沉,消耗大量的油酸钠,不利于浮选的进行。