Human thyroxine-binding globulin (TBG): Heterogeneity within individuals and among individuals demonstrated by isoelectric focusing

Isoelectric focusing of human plasma samples labeled in vitro with [¹²⁵I]-thyroxine reveals considerable biochemical and genetic variation in thyroxine-binding globulin. (1) In all individuals tested, at least three primary isoelectric bands are seen in the pH range of 4.2 to 4.5, with additional bands at lower pH ranges. Similar patterns are produced by plasma from nonhuman primates. These band differences appear to be the result of differences in sialic acid content. TBG produces a single electrophoretic band on standard polyacrylamide gel electrophoresis. (2) Genetically determined, X-linked differences in electrophoretic mobility of TBG are observed in several human populations. Female homozygotes or male hemizygotes for the TBG slow variant (TBG-S) produce band patterns shifted by 0.5 pH unit cathodal to the common pattern (TBG-C). Female heterozygotes produce patterns with six-plus bands, representing the simple sum of the common and slow types. This difference is not the result of differences in sialic acid content. The gene frequency of this variant is 10% in American Blacks. (3) In pregnant women additional anodal bands are observed, giving the impression of a shift, by integral steps, in the pattern relative to the nonpregnant type. This shift is abolished by mild neuraminidase treatment.This work was supported by a grant from the O'Brien family of Houston, Texas.     

Altered Glycoflavone expression in induced Autotetraploids of Phlox drummondii

The effects of colchicine induced autotetraploidy on non-anthocyanin flavonoid expression were determine for 15 cultivars of Phlox drummondii and for the naturally occuring P. drummondii ssp. mcallisteri. Collectively, the taxa express a total of nine glycoflavonoid derivatives (C, O-diglycosides or di-C-glycosides) of either apigenin or luteolin. The autotetraploids of 14 cultivars and those of the natural subspecies exhibit altered glycoflavone profiles relative to their respective diploid sources. The qualitative alternations in the cultivars may be grouped into three phenotypic categories: (1) the expression of novel glycoflavones, (2) the absence of diploid glycoflavones, and (3) the deregulation of tissue-specific glycoflavone production. Alterations in mcallisteri autotetraploids include only the latter two categories. Each of the novel compounds is otherwise expressed among other diploid cultivars or in other wild P. drummondii subspecies. Quantitatively, the phenolic content of most autotetraploid flowers is significantly greater than in respective diploid flowers. However, on a dry weight basis, phenolic titre in comparable 4n and 2n floral or leaf tissues is not significantly different. Floral tissues express from 5 to 10 times the phenolic titre of leaves. The results are discussed in terms of the possible origins of novel flavonoids in natural polyploid Phlox species.     

二氢乳清酸脱氢酶的结构特征和催化循环研究进展

二氢乳清酸脱氢酶是黄素依赖的线粒体酶,它催化嘧啶从头合成的第4步反应,将二氢乳清酸氧化为乳清酸。通过选择性抑制二氢乳清酸脱氢酶,从而抑制嘧啶的合成,已被开发用于治疗癌症、自身免疫性疾病、细菌或病毒感染以及寄生虫疾病等。抑制剂的开发需详细了解二氢乳清酸脱氢酶的结构特征和催化循环机制。因此,文中主要从这两个方面进行了综述,并展望了该酶的抑制剂在临床应用中的前景。     

胰腺癌的生物学临床诊断研究进展

胰腺癌(pancreatic cancer,PC)是一种发病率接近死亡率、死亡率极高的恶性肿瘤.由于胰腺癌早期无明显病症,许多病人确诊时已是癌症末期,错过了最佳的治疗时期,预后极差,因此,迫切需要高效的胰腺癌早期诊断生物标志物.随着高通量测序技术(next-generation sequencing,NGS)、高分辨质...     

MHC Class I Immunopeptidome: Past,Present, and Future

In the 35 years since the revelation that short peptides bound to major histocompatibility complex class I and II molecules are the secret of the major histocompatibility complex–restricted nature of T-cell recognition, there has been enormous progress in characterizing the immunopeptidome, the repertoire of peptide presented for immunosurveillance. Here, the major milestones in the journey are marked, the contribution of proteasome-mediated splicing to the immunopeptidome is discussed, and exciting recent findings relating the immunopeptidome to the translatome revealed by ribosome profiling (RiboSeq) is detailed. Finally, what is needed for continued progress is opined about, which includes the infusion of talented young scientists into the antigen-processing field, currently undergoing a renaissance; thanks in part to the astounding success of T-cell–based cancer immunotherapy.     

Isolation and partial amino acid sequencing of the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase from three species of orchid

Small subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) have been purified from 3 species of orchid in the genus Cymbidium by gel filtration followed by preparative sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and electroelution. The samples were subjected to amino acid composition analysis and partial N-terminal amino acid sequencing. The sequencing data clearly confirm that one of the species examined is the hybrid offspring of a cross between the other two.     

两系杂交小麦恢复系MR168抗条锈病基因遗传分析及分子标记定位

小麦条锈病是影响杂交小麦普及推广的重要因素。文章利用基因推导法和SSR分子标记技术,研究了温光型两系杂交小麦恢复系MR168的抗条锈性遗传规律及其控制基因染色体位置。结果表明,MR168对CY29、CY31、CY32、CY33等条锈菌生理小种表现高抗至免疫;对SY95-71/MR168杂交组合的正反交F1、BC1、F2和F3群体分单株接种鉴定显示,MR168对CY32号小种的抗性受1对显性核基因控制,该抗病基因来源于春小麦品种辽春10号。利用集群分离分析法(Bulked segregant analysis,BSA)和简单重复序列(Simple sequence repeat,SSR)分子标记分析抗病亲本MR168、感病亲本SY95-71及183个F2代单株,发现了与MR168抗条锈病基因连锁的5个微卫星标记Xgwm273、Xgwm18、Xbarc187、Xwmc269、Xwmc406,并将该基因初步定位在1BS着丝粒附近,暂命名为YrMR168;构建了包含YrMR168的SSR标记遗传图谱,距离YrMR168最近的两个微卫星位点是Xgwm18和Xbarc187,遗传距离分别为1.9 cM和2.4 cM,这两个微卫星标记可用于杂交小麦抗条锈病分子标记辅助育种。     

微卫星标记分析中国梨木虱种群的遗传多样性

中国梨木虱Cacopsylla chinensis (Yang et Li)是梨树主要害虫之一。为了从分子水平评估中国梨木虱种群内的遗传变异和种群间的遗传分化, 本文应用7对微卫星DNA引物对中国16个地区中国梨木虱种群进行遗传多样性分析。结果表明： 各位点有效等位基因为2.2927～10.0610, 多态信息含量(PIC)值在0.5073～0.8735之间。16个种群的平均期望杂合度为0.7876, 遗传距离在0.0951～1.0139之间, Nei氏期望杂合度为0.4771～0.7892, Shannon信息指数在0.8396～1.9989之间, 群体分化率F_ST为11.61%, 基因流平均值为2.2236。结果表明, 7个微卫星位点均具有较高的多态性, 各种群间的遗传分化水平较低, 基因交流程度较高, 遗传变异主要存在于种群内的个体间。研究结果为制定针对中国梨木虱的有效防治策略提供部分分子生物学的基础资料。     

Reporter system for the detection of in vivo gene conversion

We have devised a system for the study of in vivo gene correction based on the detection of color variants of the green fluorescent protein (GFP) from the jellyfish Aequorea victoria. The intensity and spectra of the fluorescence emitted by the blue (BFP) and red-shifted (EGFP) variants of GFP differ from each other. We modified one nucleotide from an EGFP expression vector that we predicted would yield a blue variant (TAC-CAC, Tyr⁶⁶-His⁶⁶). Cells that were either transiently or stably transfected with the reporter system were used to test the functionality and feasibility of the detection of in vivo gene correction. A thio-protected single-stranded oligonucleotide designed to convert the genotype of the blue variant to that of the EGFP variant by the correction of a single base pair was delivered to the reported cells using a variety of methodologies and strategies. Conversion events were easily observed using fluorescent microscopy because of the enhanced emission intensity and different spectra of the EGFP variant.