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71.
The infrared spectra of 3mM solutions of horse heart cytochrome c were recorded as a function of pD(corresponding to acid high spin form, acidic low spin form, native form, lysine form, the so-termed “strained lysine form” as well as the so-termed “A state” of cytochrome c). An analysis of the pH-induced changes in the secondary structure was performed based on changes in the conformation-sensitive amide I bands of this protein. In lysine and strained lysine forms, the contents of random structure increase at the expense of α-helix. In acidic low. spin form (pH4–2.5), cytochrome c was almost unfolded. The proportion of α-helix had a substantial decrease while the contents of both random structure and 310-helices got a rise. In acidic high spin form (when pH is below 2.5), a further decrease of pD gave no rise to a continued unfolding in cytochrome c but made it refold to the “A state” with properties similar to those of a molten globular state. Adding enough KC1 to the cytochrome c solution(pD2.2 with 0.5MKC1 and pD3.0 with 1.5 MKCl) in which cytochrome c was nearly fully unfolded also led to the formation of A state of cytochrome c. The compositions of all types of secondary structures in A state were evaluated. The behavior of 310-helices in acidic high/low spin form indicated they might be intermediates between α-helices and random structure in acidic solution as proposed by Miick et al. 相似文献
72.
Let C be the classical Cantor triadic set. For ${\alpha,\beta\in [-1,1]}$ , a sufficient and necessary condition for ${(C\times C)\cap (C\times C+(\alpha,\beta))}$ to be self-similar is obtained. 相似文献
73.
74.
Peide Zhao Zhidong Zhang Wenxia Bao Qing Yu Yong Zhang Zhongya Zhang Dayun Wang Ming Liu 《Optics Communications》2010,283(9):1924-1928
The two-photon absorption (TPA) coefficient (β) relating to pulse models of laser is theoretically studied based on the nonlinear absorption equation. An expression of nonlinear energy transmission is obtained, in which a factor (g) is introduced to describe the β deviation resulting from the pulse profile of laser. The relative deviation can be then expressed as (1/g − 1)% for comparing β obtained based on other pulse models of laser with β0 based on the rectangular one. The values of g factor and the deviation of some typical ultra-short pulse models used nowadays are also calculated and presented. Our results suggest that the β deviations from the temporal pulse shapes should not be neglected in usual nonlinear transmission measurement. The g factor may become a useful parameter in taking account of this deviation. 相似文献
75.
76.
Li Wenxia 《数学学报(英文版)》1998,14(4):487-494
Corresponding to the irreducible 0–1 matrix (a
ij
)
n×n
, take similitude contraction mappingsϕ
ij
for eacha
ij
=1, ina
ij
=1, in R
d
with ratio 0<r
ij
<1. There are unique nonempty compact setsF
1,…,F
n
satisfying for each1≤i≤n, F
i. We prove that open set condition holds if and only ifF
i
is ans-set for some1≤i≤n, wheres is such that the spectral radius of matrix (r
ij
3
)
n x n
is 1.
Partly supported by Natural Science Foundation of China, and partly by Natural Science Foundation of Hubei Province 相似文献
77.
Wenxia Pan Wenhong Zhang Wei Ma Chengkang Wu 《Plasma Chemistry and Plasma Processing》2002,22(2):271-283
Argon DC plasma jets in stable laminar flow were generated at atmospheric pressure with a specially designed torch under carefully balanced generating conditions. Compared with turbulent jets of short length with expanded radial appearance and high working noise, the laminar jet could be 550 mm in length with almost unchanged diameter along the whole length and very low noise. At gas feeding rate of 120 cm3/s, the jet length increases with increasing arc current in the range of 70–200 A, and thermal efficiency decreases slightly at first and then leveled off. With increasing gas flow rate, thermal efficiency of the laminar jets increases and could reach about 40%, when the arc current is kept at 200 A. Gauge pressure distributions of the jets impinging on a flat plate were measured. The maximum gauge pressure value of a laminar jet at low gas feeding rate is much lower than that of a turbulent jet. The low pressure acting on the material surface is favorable for surface cladding of metals, whereas the high pressure associated with turbulent jets will break down the melt pool. 相似文献
78.
辅酶B12模型化合物的研究——Ⅰ.双水杨醛缩乙二亚胺烷基钴(Ⅲ)配合物Co-C键的性质 总被引:5,自引:1,他引:5
本工作合成、表征了一系列辅酶B12模型化合物RCo(Salen)L,其中R=CH3,C2H5,n和i-C3H7,n和i-C4H9,研究了上述配合物固体和溶液的Co-C键稳定性,结果表明:固体配合物Co-C键断裂的温度受烷基位阻影响,它们具有以下顺序:CH3>C2H5>n-C3H7≈n-C4H9≈i-C4H9≈i-C3H7.此外还确定了影响配合物Co-C键在溶液中稳定性的因素. 相似文献
79.
二高氯酸根.(二亚乙基三胺).咪唑合铜(Ⅱ)的合成与结构 总被引:1,自引:0,他引:1
已知多种金属酶和金属蛋白中的金属离子与肽链上的组氨酸残基的咪唑基配位构成其活性中心的重要部分。在Cu、Zn超氧化物歧化酶和细胞色素C氧化酶a_3中、组氨酸的咪唑基成为连接Cu、Zn或Cu、Fe原子的桥基尤为突出。作为超氧化物歧化酶活性中心结构与性能关联研究的一部分,我们首先合成一初级物[Cu(ImH)(dien)(ClO_4)_2并用X光单晶衍射测定了它的结构。按衍射系统消光,晶体属于正交晶系空间群Pna2_1或Pnma。由于分子中重原子的特殊分布和咪唑环的无序取向,按这两个空间群均可得到晶体结构相近的解析结果,从而面临在有心和无心空间群对之间作出选择这一棘手问题。本文主要报导按Pnma求解结构和分子结构的特征。 相似文献
80.