斑头雁(Anser indicus)高铁血红蛋白的晶体生长和初步的X-射线衍射研究

本文报导了斑头雁(Auser indicus)高铁血红蛋白的晶体生长和初步的晶体学研究.晶体的衍射分辨率为2.5A或更好,四方晶系.空间群为P4:2_12,晶胞参数为:a=b=80.8A,e=107.3A,V=700523A~3.每个晶胞中含4个四聚体分子,每个不对称单位中含半个四聚体分子.     

灰雁(Anser anser)氧合血红蛋白的晶体生长和X射线衍射的初步分析

灰雁血红蛋白分子与斑头雁血红蛋白分子结构相近,二者对比有助于分析斑头雁血红蛋白的高氧亲和性机理。本文报道了以聚乙二醇６,０００为沉淀剂生长出灰雁氧合血红蛋白的晶体,经Ｘ射线衍射分析确定,晶体属单斜晶系,空间群为Ｐ２１,晶胞参数为ａ＝５．７５５２ｎｍ,ｂ＝８．０６２４ｎｍ,ｃ＝７．２５７１ｎｍ,α＝９０°,β＝１０２．７５°,γ＝９０°,晶胞体积为３．２８×１０２ｎｍ３,每个不对称单位中包含一个四聚体分子。研究灰雁氧合血红蛋白的晶体结构,可以得到较准确的结构信息。     

北京鸭(Anas platyrhynchos)氧合血红蛋白的晶体生长和X射线晶体学的初步研究

北京鸭氧合血红蛋白晶体在以聚乙二醇６０００为沉淀剂,在ｐＨ７．１,血红蛋白浓度为２５ｍｇ／ｍｌ条件下采用一批结晶法培养得到,并且适合于Ｘ射线衍射分析。经Ｘ射线平面探测仪收集衍射强度数据和处理,确定晶体属四方晶系,空间群为Ｐ４２２１２,晶胞参数为ａ＝ｂ＝８．１１３ｎｍ,ｃ＝１０．７０７ｎｍ,α＝β＝γ＝９０°,每个不对称单位中包含半个四聚体分子。进一步得到北京鸭氧合血红蛋白高分辨率晶体结构,通过与其高海拔同类－斑头雁分析比较深入研究斑头雁血红蛋白分子的高氧亲和性机制。     

X-射线纤维衍射在多糖构型分析中应用的研究进展

本文从Ｘ射线纤维衍射法的原理,实验方法及应用实例三个方面对该方法在多糖构型分析中的应用状况进行综述,引用文献２０篇。     

斑头雁脱氧血红蛋白的晶体生长及X射线晶体学的初步研究

报导了以Ｎａ２Ｓ２Ｏ４为还原剂制备脱氧血红蛋白,并以聚乙二醇溶液为沉淀剂,在ｐＨ７．２,蛋白浓度２０ｍｇ／ｍｌ条件下培养出适合于Ｘ射线分析用的斑头雁脱氧血红蛋白晶体,经Ｘ射线平面探测仪收集衍射强度数据和处理。确定晶体属三斜晶系,空间群Ｐ１,晶胞参数α＝７．０９ｎｍ,ｂ＝９．５４ｎｍ,ｃ＝５．８７ｎｍ,α＝７２．８°,β＝６５．９°,γ＝８２．０°,ｖ－３４６．１ｎｍ３,每个不对称单位包含２个四聚体分子,共收集２．８分辨率的独立衍射点３０６５４个,Ｒｍ因子为５．１４％。     

综述: X射线晶体衍射是解析出青蒿素三维结构的唯一方法

X射线晶体衍射是解析出青蒿素三维结构的唯一方法     

斑头雁(Auser Indicus)氧合血红蛋白的结晶和X射线的初步分析

本文报道了以聚乙二醇溶液为沉淀剂培养斑头雁氧合血红蛋白晶体.经X射线旋进照相法分析确定,晶体属四方晶系,空间群为P4_22_12,晶胞参数a=b=81.5(?),c=106.4(?),α=β=γ=90V=706735.4(?)~3.每个不对称单位内包含半个四聚体分子.     

用X-粉晶衍射法研究氨基酸配合物

研究了金属钴离子与Ｌ－赖氨酸配合物的合成方法,并用Ｘ－粉晶衍射对钴离子氨基酸配合物进行了分析鉴定。     

青霉素G酰化酶制备,晶体生长及初步晶体学研究

用基因工程菌Ｅ．ＣｏｌｉＡＥ１０９生产了青霉素Ｇ酰化酶,该酶经分离纯化后,摸索了晶体生长条件。用ＰＥＧ８０００作为沉淀剂以两种方法获得了晶体。晶体衍射能力超过２．０,初步晶体学研究显示晶胞参数ａ＝５２．１９,ｂ＝６９．３５,ｃ＝７３．９０,α＝６８．８０°,β＝７１．４０°,γ＝７４．２０°,空间群Ｐ１,收集了一套２．５分辨率的数据。     

ELECTRON MICROSCOPE AND LOW-ANGLE X-RAY DIFFRACTION STUDIES OF THE NERVE MYELIN SHEATH

1. A close correlation has been obtained between high resolution electron microscopy and low-angle x-ray diffraction studies of the myelin sheath of frog and rat peripheral and central nerves. Extensive studies were performed by application of both techniques to the same specimens, prepared for examination by OsO₄ or KMnO₄ fixation, and embedding either in methacrylate or in gelatin employing a new procedure. Controlled physical and chemical modifications of the myelin sheath prior to fixation were also investigated. 2. A correspondence was established between the layer spacings observed in electron micrographs and the fundamental radial repeating unit indicated by the low-angle x-ray diffraction patterns. The variations in relative intensities of the low-angle x-ray reflections could be related to the radial density distributions seen in the electron micrographs. 3. An analysis of the preparation procedures revealed that OsO₄ fixation introduces a greater shrinkage of the layer spacings and more pronounced changes in the density distribution within the layers than KMnO₄ fixation. The effects of methacrylate and gelatin embedding are described, and their relative merits considered in relation to the preservation of myelin structure by OsO₄ fixation. 4. The experimental modifications introduced by freezing and thawing of fresh whole nerve are described, particularly the enhancement of the intermediate lines and the dissociation of the layer components in the myelin sheath. A characteristic collapsing of the radial period of the sheath is observed after subjecting fresh nerve trunks to prolonged and intense ultracentrifugation. 5. Controlled extraction of fresh nerve with acetone at 0°C., which preferentially removes cholesterol, produces characteristic, differentiated modifications of the myelin sheath structure. Electron microscopy reveals several types of modifications within a single preparation, including both expanded and collapsed layer systems, and internal rearrangements of the layer components. Alcohol extraction leads to a more extensive structural breakdown, but in certain areas collapsed layer systems can still be observed. The components of the lipide extracts could be identified by means of x-ray diffraction. These modifications emphasize the importance of cholesterol in the myelin structure, and disclose a resistance of the dense osmiophilic lines to lipide solvents. 6. The significance of these structures is discussed in relation to present concepts of the molecular organization of myelin. The available evidence is consistent with the suggestion that the primary site of osmium deposition is at the lipoprotein interfaces and that the light bands probably represent regions occupied by lipide chains. The electron microscope and x-ray diffraction data also indicate the possibility of a regular organization within the plane of the layers, probably involving units of 60 to 80 A. The myelin sheath is regarded as a favourable cell membrane model for detailed analysis by combined application of x-ray diffraction and electron microscopy.     

X-RAY DIFFRACTION STUDIES ON FROG MUSCLES

1. X-ray diffraction studies of sartorius muscles of Rana pipiens were made in a new x-ray diffraction camera which permits exposures of 3 to 6 minutes. The object-film distance can be varied from 20 to 80 mm; the muscle inside the camera can be electrically stimulated while contracting isotonically or isometrically, and can be observed by a special device. After exposures up to 30 minutes (approximately 40,830 r) muscles are still alive and responsive. 2. Contrary to the x-ray diffraction pattern of powdered dry muscle, which pattern consists of two rings corresponding to spacings of 4.46 Å.u. and 9.66 Å.u., both moist and dried whole sartorius muscle show signs of orientation in both rings, consisting of two equatorial streaks (wet) or points (dry) and meridional sickles. The moist muscle shows in addition a diffuse water ring. The spacings corresponding to the orientation points and elliptical structure show only slight differences in moist and dried samples. Through statistical computations based on two different series consisting of thirteen moist and twenty-eight dried samples, and nine muscles before and after drying, it was shown that only the divergence in the smaller spacing has some real significance, which indicates that most water of the moist muscle is bound intermolecularly. Upon resoaking of dried muscle the x-ray diffraction pattern of the moist muscle is restored. 3. Stretching of muscle by weights below the breaking point produces an additional well defined diffraction line, corresponding to a spacing of 4.32 Å.u. A similar diffraction line can be produced in frog tendon upon stretching. 4. The influence of heat on the x-ray diffraction pattern of muscle depends upon the maximum temperature and the length of action; 5 minutes at 50° C. markedly reduces the orientation of the sample; 5 minutes'' immersion in boiling Ringer''s solution destroys the orientation and produces a ring corresponding to a spacing of 5.3 to 5.5 Å.u. in the moist and sharpening of the backbone reflection in the dried specimen. 5. Ultraviolet light brings forth changes in the x-ray diffraction pattern varying with the intensity of the irradiation. Ultimately a disappearance of the equatorial points and of the outside sickles is achieved while the elliptical shape of the outside ring and its diffuseness persist. In addition two salt rings characteristic of NaCl indicate that the irradiated muscles have become permeable to the surrounding medium (Ringer''s solution). 6. Both faradic and single shock electrical stimulation were tried on muscles. If shortening of the muscle is prevented either by sufficient weight or by tying the muscle in a frame, no changes in the x-ray diffraction pattern occur; if the muscle is allowed to shorten without weights or by using insufficient weights, then the orientation either disappears completely or partially. When the muscle is stretched while contracted by electrical stimulation the orientation of the x-ray diffraction pattern reappears. 7. A number of salts with uni- and bivalent ions in concentrations corresponding osmotically to 0.73 per cent NaCl and 10 per cent NH₄Cl were studied in their effects upon the x-ray diffraction of muscles. Of the salts with univalent ions in the lower concentration only KCl causes a marked decrease of orientation and an increase in the permeability of the fiber membranes. Similar effects on the orientation seem to be produced by CaCl₂ while MgCl₂ causes rather a more pronounced orientation. At hypertonic salt concentrations the orientation disappears completely and the corresponding salt rings become visible. Besides, NaCNS seems to have a specific effect on the outside ring and LiCl produces a ring at 21.3 Å.u. and a splitting of the outside ring. 8. Strong mineral and lactic acids in concentrations up to 0.005 N have little if any influence upon the x-ray diffraction of muscles. A further increase in acidity to 0.01 N and above destroys the orientation completely, causes sharpening of the backbone reflection, and increased membrane permeability. These changes are irreversible upon neutralization. Also the effects of swelling upon the water ring of fresh muscle become manifest. Weak acids at higher concentrations show an effect similar to that of strong acids. 9. Rigor mortis produces a more or less complete loss of orientation. The muscles show signs of increased permeability. 10. Alkalies destroy the orientation of the x-ray diffraction pattern. The effective concentration is higher than the corresponding amount of acid. 11. Formaldehyde produces only minor changes in the x-ray diffraction patterns of muscles. 12. The effects of alcohol depend primarily upon the concentration applied. Low concentrations (5 per cent) seem to have a passing stimulating effect, at concentrations of 15 per cent, the anesthetizing effect becomes manifest in well defined orientation. The diameter of the water ring is reduced. If 95 per cent alcohol is allowed to act upon muscle for more than 12 minutes, then the orientation disappears completely and the backbone spacing becomes as sharp as in boiled muscle. 13. The effects of chloroform depend upon whether the muscle is allowed to contract or not. Only if the muscle is allowed to contract in chloroform-saturated Ringer''s solution is the orientation lost and salt rings appear as well as a ring corresponding to a spacing of 22 Å.u,, which has been observed in other changes in muscles. 14. In muscles allowed to shorten in a caffeine-Ringer''s solution the orientation disappears, salt rings become visible as well as a decrease in size of the water ring; a new arc corresponding to a spacing of 4.18 Å.u. was observed in one case.     

ELECTRON MICROSCOPE AND X-RAY DIFFRACTION STUDIES ON A HOMOLOGOUS SERIES OF SATURATED PHOSPHATIDYLCHOLINES

Three homologous saturated phosphatidylcholines were studied by electron microscopy after tricomplex fixation. The results are compared with those obtained by x-ray diffraction analysis of the same and some other homologous compounds, in the dry crystalline state and after tricomplex fixation. By electron microscopy alternating dark and light bands are observed which are likely to correspond to phosphatide double layers. X-Ray diffraction reveals the presence of lamellar structures of regular spacing. The layer spacings obtained by both methods are in good agreement. From the electron micrographs the width of the polar parts of the double layers can be derived directly. The width of the carboxylglycerylphosphorylcholine moiety of the layers is found by extrapolating the x-ray diffraction data to zero chain length of the fatty acids. When from this width the contribution of the carboxylglyceryl part of the molecules is subtracted, again we find good agreement with the electron microscope measurements. An attempt has been made to account for the different layer spacings measured in terms of orientation of the molecules within the double layers.     

枯草杆菌蛋白酶E的结晶及初步衍射研究

对来源于枯草芽孢杆菌的枯草杆菌蛋白酶E进行了初步晶体学研究。应用悬滴汽相扩散法生长出了该酶的单晶体,其空间群为P2_12_12_1,晶胞边长a=74.35A,b=80.98A,c=88.59A。已用面探测器衍射仪收集了一套中等分辨率的X射线衍射数据。     

LIFE HISTORY STUDIES OF THE LESSER SNOW GOOSE (ANSER CAERULESCENS CAERULESCENS). VI. PLUMAGE POLYMORPHISM,ASSORTATIVE MATING AND FITNESS

The investigated the hypothesis that positive assortative mating for plumage coloration observed in populations of the dichromatic Lesser Snow Goose (Anser caerulescens caerulescens) evolved and persists due to selective advantages accruing to individuals choosing mates phenotypically similar to themselves. We examined potential differences between pure (white × white, blue × blue) and mixed (white × blue, blue × white) pairs for an array of fitness components related to both fecundity and viability. While no differences were detected for most components, mixed pairs consistently enjoyed enhanced nesting success relative to their pure counterparts. In addition, pre-reproductive viability and female offspring recruitment were significantly greater for mixed pairs for some of the cohorts examined. Not only have we failed to find enhanced reproductive success associated with positive assortment, we have provided evidence that there is some advantage associated with negative assortment. In light of our findings, we suggest: 1) that positive assortment results from the use of familial color as one element in species recognition; 2) that the enhanced fitness of mixed pairs, particularly with respect to nesting success, results from complementation of parental behavior; and 3) that while negative assortment will not likely become the rule in this population, the selective advantage of mixed pairs is a potential determinant of pair type frequencies in the La Pérouse Bay population.