Human Calprotectin： Effect of Calcium and Zinc on its Secondary and Tertiary Structures, and Role of pH in its Thermal Stability

Calprotectin, a heterodimeric complex belonging to the S 100 protein family, has been found predominantly in the cytosolic fraction of neutrophils. In the present study, human calprotectin was purified from neutrophils using two-step ion exchange chromatography. The purified protein was used for circular dichroism study and fluorescence analysis in the presence of calcium and zinc at physiological concentrations, as well as for assessment of its inhibitory activity on the K562 leukemia cell line. The thermal stability of the protein at pH 7.0 （physiological pH） and 8.0 （similar to intestinal pH） was also compared. The results of cell proliferation analysis revealed that human calprotectin initiated growth inhibition of the tumor cells in a dose- dependent manner. The intrinsic fluorescence emission spectra of human calprotectin （50 ktg/ml） in the presence of calcium and zinc ions show a reduction in fluorescence intensity, reflecting a conformational change within the protein with exposure of aromatic residues to the protein surface that is important for the biological function of calprotectin. The far ultraviolet-circular dichroism spectra of human calprotectin in the presence of calcium and zinc ions at physiological concentrations show a decrease in the m-helical content of the protein and an increase in [3- and other structures. Our results also show that increasing the pH level from 7.0 to 8.0 leads to a marked elevation in the thermal stability of human calprotectin, indicating a significant role for pH in the stability of calprotectin in the gut.     

钙、镁、硫元素对浙贝母生长及产量品质的影响

目的：研究不同浓度的钙、镁和硫元素对浙贝母生长和产量品质的影响,为浙贝母的合理、高效栽培提供理论依据。方法：采用盆栽土培的方法,对钙、镁、硫元素分别设置0 mg/kg、40 mg/kg、80 mg/kg、160 mg/kg浓度水平的处理组,对浙贝母产量品质、植株生长及根际土壤理化性质进行测定。结果：与对照组（CK）相比,多数施加钙、镁、硫元素对处理组浙贝母鳞茎产量有增加效果,平均增加12.20%;浙贝母鳞茎中贝母素甲、贝母素乙、贝母辛和总生物碱含量除Mg(40 mg/kg)组外均有增加,与CK组比较分别平均增加26.01%、41.24%、42.61%和15.27%,Ca(80mg/kg)、Mg(160 mg/kg)和S(40 mg/kg)组的浙贝母产量和品质最佳;S(160 mg/kg)组浙贝母茎粗较CK组有显著增加;Ca(80 mg/kg)处理叶中类胡萝卜素和叶绿素a含量显著高于CK组,Ca(80 mg/kg)、S(80 mg/kg)和S(160 mg/kg)处理叶中叶绿素b和叶绿素总量显著高于CK组;不同浓度的钙镁硫处理均能显著提高浙贝母根际土壤中有机物的含量,钙的施用能显著提高土...     

飘香藤离体培养中茎尖枯死现象的控制

茎尖枯死或枝叶枯萎是由植物生理调节混乱而引起的一种普遍现象。茎尖枯死现象的出现,可能是钙元素的缺乏引起的,硼的缺乏也会引起这一现象。因此怎样防止这一现象的发生,是组织培养中十分关注的问题。本文以飘香藤（Mandevilla sanderi Hemsl．）离体培养的不定芽为材料,对茎尖枯死的控制和对优质芽的保护进行了研究。     

Mycobacterial PE_PGRS Proteins Contain Calcium-Binding Motifs with Parallel β-roll Folds

The PE_PGRS family of proteins unique to mycobacteria is demonstrated to con- rain multiple calcium-binding and glycine-rich sequence motifs GGXGXD/NXUX. This sequence repeat constitutes a calcium-binding parallel/3-roll or parallel β-helix structure and is found in RTX toxins secreted by many Gram-negative bacteria. It is predicted that the highly homologous PE_PGRS proteins containing multiple copies of the nona-peptide motif could fold into similar calcium-binding structures. The implication of the predicted calcium-binding property of PE_PGRS proteins in the Ught of macrophage-pathogen interaction and pathogenesis is presented.