Binding of the Zn2+ ion to ferric uptake regulation protein from E. coli and the competition with Fe2+ binding: a molecular modeling study of the effect on DNA binding and conformational changes of Fur

The three dimensional structure of Ferric uptake regulation protein dimer from E. coli, determined by molecular modeling, was docked on a DNA fragment (iron box) and Zn²⁺ ions were added in two steps. The first step involved the binding of one Zn²⁺ ion to what is known as the zinc site which consists of the residues Cys 92, Cys 95, Asp 137, Asp141, Arg139, Glu 140, His 145 and His 143 with an average metal-Nitrogen distance of 2.5 Å and metal-oxygen distance of 3.1–3.2 Å. The second Zn²⁺ ion is bound to the iron activating site formed from the residues Ile 50, His 71, Asn 72, Gly 97, Asp 105 and Ala 109. The binding of the second Zn²⁺ ion strengthened the binding of the first ion as indicated by the shortening of the zinc-residue distances. Fe²⁺, when added to the complex consisting of 2Zn²⁺/Fur dimer/DNA, replaced the Zn²⁺ ion in the zinc site and when a second Fe²⁺ was added, it replaced the second zinc ion in the iron activating site. The binding of both zinc and iron ions induced a similar change in Fur conformations, but shifted residues closer to DNA in a different manner. This is discussed along with a possible role for the Zn²⁺ ion in the Fur dimer binding of DNA in its repressor activity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

缺锌儿童的舌苔改变及其分析

从中医舌诊角度对193例缺锌儿童舌苔改变作了临床观察及理论分析,认为人体内微量元素锌与舌苔之间存在着有机联系,锌的吸收障碍由脾、胃功能失司引起,相应地引起舌苔的改变,大多数表现为“地图舌”。发现“地图舌”患儿在其他临床症状方面与机体“缺锌”状态表现出来的症状相似,而且病因相同,在病理机制及组织学方面曲解释一致,且用“锌”制剂治疗后,“地图舌”明显很快地消失或得到改变。笔者提出,“地图舌”可以作为机体缺锌的临床体征之一,本文为此提供了初步的理论依据。     

Determination of total mercury in human hair and animal fur by combustion atomic absorption spectrometry

A commercially available mercury (Hg) analyzer based on sample combustion, gold amalgamation, and atomic absorption spectrometry (AAS) was evaluated for the direct determination of Hg in composites of human hair and individual samples of horse fur. Results for human hair reference material (NIES No. 13) were within the certified range. Analyses of “blind” samples from an international interlaboratory (n>16) comparison study produced results within 1S.D. of the consensus means. Precision (%R.S.D.) was found to be <5% and total analyses time per sample was <10 min. This study demonstrated that analyzers based on combustion-AAS are suitable for wide-scale monitoring of Hg in human hair and animal fur.     

家猫针毛的形态研究和X射线能谱元素分析

本文对家猫针毛的形态结构进行了扫描电镜（ＳＥＭ）观察,并且利用Ｘ射线能谱仪（ＥＤＡＸ）分别为鳞片层、皮质层和髓质层进行了元素分析。结果表明：家猫针毛具有特殊的形态结构,针毛纤维各层间所含元素有明显区别。可为家猫针毛的性能研究及鉴别提供依据。     

A hierarchical screening method for detection of illegal adulterants in Fur seal ginseng pills by profiling analysis of HPLC multi‐dimensional fingerprints

A novel method for hierarchical screening of illegal adulterants in Fur seal ginseng pills products was developed by multi‐dimensional fingerprint profiling analysis. Fingerprint feature of the samples was acquired by high‐performance liquid chromatography analysis of 11 batches of samples with diode array detector and fluorescence detector, and then potential illegal adulterants including phosphodiesterase type‐5 inhibitors, androgens, α receptor antagonists and yohimbine, were further separated at multiple wavelengths to reduce or remove interferences from sample matrix for highlight their chromatographic characteristics. Accordingly, a hierarchical screening strategy was designed by first‐order and second‐order fingerprints combined with spectral examination to achieve high accuracy and reliability. The method was successfully applied to screening of illegal adulterants in real samples, and it also exhibited good quantification performance through validation tests. From 16 batches of samples, three suspected samples were confirmed to be positive, containing 9.37μg/g of testosterone, 18.8 μg/g of tadalafil, and 48.5 μg/g of sildenafil, respectively. The recoveries and relative standard deviations were in the range of 83.6–103.1% and 4.2–6.8%, respectively. The proposed method provided a simple, efficient and promising alternative to monitoring functional foods.