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Manjula BN Tsai AG Intaglietta M Tsai CH Ho C Smith PK Perumalsamy K Kanika ND Friedman JM Acharya SA 《The protein journal》2005,24(3):133-146
PEGylation induced changes in molecular volume and solution properties of HbA have been implicated as potential modulators of its vasoconstrictive activity. However, our recent studies with PEGylated Hbs carrying two PEG chains/Hb, have demonstrated that the modulation of the vasoconstrictive activity of Hb is not a direct correlate of the molecular volume and solution properties of the PEGylated Hb and implicated a role for the surface charge and/or the pattern of surface decoration of Hb with PEG. HbA has now been modified by thiolation mediated maleimide chemistry based PEGylation that does not alter its surface charge and conjugates multiple copies of PEG5K chains. This protocol has been optimized to generate a PEGylated Hb, (SP-PEG5K)6-Hb, that carries ~six PEG5K chains/Hb – HexaPEGylated Hb. PEGylation increased the O2 affinity of Hb and desensitized the molecule for the influence of ionic strength, pH, and allosteric effectors, presumably a consequence of the hydrated PEG-shell generated around the protein. The total PEG mass in (SP-PEG5K)6-Hb, its molecular volume, O2 affinity and solution properties are similar to that of another PEGylated Hb, (SP-PEG20K)2-Hb, that carries two PEG20K chains/Hb. However, (SP-PEG5K)6-Hb exhibited significantly reduced vasoconstriction mediated response than (SP-PEG20K)2-Hb. These results demonstrate that the enhanced molecular size and solution properties achieved through the conjugation of multiple copies of small PEG chains to Hb is more effective in decreasing its vasoconstrictive activity than that achieved through the conjugation of a comparable PEG mass using a small number of large PEG chains. 相似文献
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不同干扰强度生境中啮齿动物对苦槠种子的取食和扩散 总被引:1,自引:0,他引:1
在浙江省千岛湖地区,选择了受人类活动干扰较轻、中度和严重的3个生境,采用金属片标记法研究了啮齿动物对苦槠种子的取食和扩散.结果表明:在研究点捕获的取食种子的啮齿动物为针毛鼠( Niviventer fulvescens),尽管捕获的数量少,但种子被取食和扩散的速率很快,3个样地内的种子均在2d内被取食或扩散完毕;中等干扰强度的生境中,被就地取食的种子最多,占鉴别种子总数的37.8%.种子扩散距离大多<5m,最大扩散距离为24.76m,3个样地种子扩散均符合负指数分布,且样地间没有显著差异;饱满种子与虫蛀种子被就地取食与搬运后取食的命运没有显著差异,但饱满种子的最大扩散距离均显著大于虫蛀种子(P<0.05),除中等干扰样地中饱满种子与虫蛀种子平均扩散距离没有显著差异外,其余2个样地中饱满种子的平均扩散距离均显著大于虫蛀种子,显示啮齿动物对饱满种子与虫蛀种子有一定的区分能力. 相似文献
135.
Save your host,save yourself? Caste‐ratio adjustment in a parasite with division of labor and snail host survival following shell damage 下载免费PDF全文
Shell damage and parasitic infections are frequent in gastropods, influencing key snail host life‐history traits such as survival, growth, and reproduction. However, their interactions and potential effects on hosts and parasites have never been tested. Host–parasite interactions are particularly interesting in the context of the recently discovered division of labor in trematodes infecting marine snails. Some species have colonies consisting of two different castes present at varying ratios; reproductive members and nonreproductive soldiers specialized in defending the colony. We assessed snail host survival, growth, and shell regeneration in interaction with infections by two trematode species, Philophthalmus sp. and Maritrema novaezealandense, following damage to the shell in the New Zealand mud snail Zeacumantus subcarinatus. We concomitantly assessed caste‐ratio adjustment between nonreproductive soldiers and reproductive members in colonies of the trematode Philophthalmus sp. in response to interspecific competition and shell damage to its snail host. Shell damage, but not parasitic infection, significantly increased snail mortality, likely due to secondary infections by pathogens. However, trematode infection and shell damage did not negatively affect shell regeneration or growth in Z. subcarinatus; infected snails actually produced more new shell than their uninfected counterparts. Both interspecific competition and shell damage to the snail host induced caste‐ratio adjustment in Philophthalmus sp. colonies. The proportion of nonreproductive soldiers increased in response to interspecific competition and host shell damage, likely to defend the parasite colony and potentially the snail host against increasing threats. These results indicate that secondary infections by pathogens following shell damage to snails both significantly increased snail mortality and induced caste‐ratio adjustments in parasites. This is the first evidence that parasites with a division of labor may be able to produce nonreproductive soldiers according to environmental factors other than interspecific competition with other parasites. 相似文献
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Molecular and morphological divergence in a stygobiont gastropod lineage (Truncatelloidea,Moitessieriidae, Paladilhiopsis) within an isolated karstic area in the Mecsek Mountains (Hungary) 下载免费PDF全文
Dorottya Angyal Gergely Balázs Virág Krízsik Gábor Herczeg Zoltán Fehér 《Journal of Zoological Systematics and Evolutionary Research》2018,56(4):493-504
Truncatelloid gastropods are one of the most species‐rich subterranean invertebrate groups. Their current taxonomy is based on morphological characters. However, this is not a comprehensive approach and does not take into account the degree of phylogenetic divergence between stygobiont populations inhabiting hydrologically isolated but geographically close caves. We studied two Paladilhiopsis populations of a small and isolated karstic area (Mecsek Mountains, Hungary) with two hydrologically separated cave systems, investigating morphological (shell morphometrics) and genetic (COI, 16S) divergence together. The populations differed both morphologically and genetically: we found strong divergence in the relative width of the shell (best described by the variable “shell angle”) and a 6.4% divergence in COI. This provides strong support for the presence of two distinct taxa; however, it is still doubtful whether they differ at the species or the subspecies level. In one of the caves, we found representatives of both haplotypes (and phenotypes), which can be explained by secondary contact after an allopatric divergence. 相似文献
138.
Analysis of Vibrio seventh pandemic island II and novel genomic islands in relation to attachment sequences among a wide variety of Vibrio cholerae strains 下载免费PDF全文
Tuan Hai Nguyen Tho Duc Pham Naomi Higa Hanako Iwashita Taichiro Takemura Makoto Ohnishi Kouichi Morita Tetsu Yamashiro 《Microbiology and immunology》2018,62(3):150-157
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为研究海南产白唇竹叶青蛇分类地位,捕捉来自海南岛各地的12个白唇竹叶青蛇样本,并从GenBank下载65个竹叶青蛇的样本序列,以瘤鼻蝮蛇为外群,建立16S系统发育树。系统发育树显示,竹叶青蛇分为多个属的观点具有很大的合理性,白唇竹叶青蛇隶属于帝汶(岛屿)竹叶青蛇属。进一步验证了经典形态学和生物地理学的观点,海南岛产白唇竹叶青与其它地方产白唇竹叶青蛇不存在生殖隔离。 相似文献