水稻种子萌发过程中α—淀粉酶与萌发速率关系的分析

用丙烯酰胺凝胶电泳技术和3,5－二硝基水杨酸（DNS）测定还原糖法,对不同萌发时间农垦58F,农垦58S和农垦58种子胚中α－淀粉酶同工酶及其酶活性变化进行研究,0－36小时萌发过程中,农垦58F和农垦58Sα-淀粉酶活性高于农垦58。胚中检测出五条酶,A2,A4和A5为上述种子共有酶带,A3为农垦58F和农垦58S特异性酶带,A1为农垦58特异性酶带,据此认为α-淀粉酶对水稻种子萌发速度起重要调控作用,A1和A3可能是调控种子发芽快慢的重要酶分子。     

Relation between the mode of binding of nitrite and the energy distribution between the two photosystems

The reversibility of nitrite-induced inhibition in relation to energy distribution between the two photosystems was studied in spinach thylakoid membranes. Measurements of electron transfer rate catalyzed by photosystem I (PS I) and photosystem II (PS II), chlorophyll a (Chl a ) fluorescence induction kinetics, S₂ state multiline spectra, and room temperature electron paramagnetic resonance (EPR) signals indicated that nitrite anions bind PS II in two ways: dissociable (loose) and non-dissociable (tight). The inhibition caused by the dissociable binding was reversible in washed (nitrite-treated samples washed with nitrite-free medium) samples, while the inhibition caused by the non-dissociable binding was irreversible. At 77 K, an increase in absorption cross section of PS I (as inferred from the excitation spectra of Chl a fluorescence) and a decrease in absorption cross section of PS II in nitrite-treated sample when compared with sample washed with nitrite-free medium and control sample suggested that nitrite plays a role in regulating the distribution of absorbed excitation energy between the two photosystems. We propose, for the first time, that the removal of loosely bound nitrite leads to migration of light-harvesting complex II back to the PS II, and thus the mode of binding of nitrite regulates the extent of migration of antenna molecules between the two photosystems.     

Relationship between the effectiveness of the antitumor action of sarcolysine and the latency period between transplantation and tumor appearance

Sarcoma induced with 3-methylcholantrene in mice was transplanted to syngeneic recipients. The latent period of the tumour growth varied from 7 to 26 days. Sarcolysine was injected once when the tumour became palpable. When the tumours were revealed 7 to 8 and 10 to 15 days after the inoculation, the tumour growth inhibition was accompanied by increased survival of mice, particularly marked at the latter period. When the tumours were revealed 17 to 20 or 22 to 26 days after the transplantation, inhibition of the tumour growth was not accompanied by any increase of survival.     

Similarities between the faces of parents and offspring in Bewick's swan and the differences between mates

The faces of individual Bewick's swans ( Cygnus columbianus bewickii ) are highly distinctive. Similarities between the faces of parents and their offspring in 12 families living in the wild were examined using a code that gave a value to 29 features of each individual's face. The similarities between the faces of 22 wild–living mated pairs were also analyzed. The offspring resembled both their parents more closely than would have been expected on a chance basis. The similarities were particularly striking in the upper part of the bill. Mates, on the other hand, did not resemble each other and analysis of each character suggested that in some respects, they were less like each other than would have been expected on a chance basis. It is concluded that the facial appearance of Bewick's swans is inherited and that the swans may actively outbreed.     

Relation between the toxic killing of mouse small intestine enterocytes and the interval between the administration of the S-specific agent hydroxyurea

The dependence of small intestinal lesions on the interval between repeated regular injections of hydroxyurea was studied. The doses of 1 g/kg and 0.2 g/kg were used. To activate the enterocyte proliferation the mice were pre-irradiated at 2 Gy. 3-4 hours after the last hydroxyurea injection the two distinct minimum points of epithelial lesions were observed at interinjection intervals of 9 and 16.5 hours. The result was dose-independent.     

mRNA两末端的相互作用

50年代,随着分子生物学中心法则的提出,掀起了蛋白质合成研究热潮。60年代末出现的ｍＲＮＡ闭环翻译模型认为,通过ｍＲＮＡ两末端相互作用形成闭环进行翻译是最高效的翻译方式。真核生物ｍＲＮＡ除了具有5′端帽子结构(ｍ7ＧｐｐｐＮ)外[1],大多还具有3′端ｐｏｌｙＡ,它们的协同作用是ｍＲＮＡ高效翻译所必需[2、3]。帽子结合蛋白(ｃａｐｂｉｎｄｉｎｇｐｒｏｔｅｉｎ,ＣＢＰ)和ｐｏｌｙＡ结合蛋白(ｐｏｌｙＡｂｉｎｄｉｎｇｐｒｏｔｅｉｎ,ＰＡＢＰ)等的发现为该假说提供了一些依据。因此,对ｍＲＮＡ两末端及其相互作用的研究引起了许多研…     

Generalized dimension of the intersection between EEGs

 The generalized dimension defined by [Mandelbrot (1995) J Fourier Anal Appl special J.P. Kahane issue: 409–432] was applied to studying the interrelationship between various parts of human cerebral cortex in different functional conditions. Taking EEG signals from different brain areas as different sets, the generalized dimensions of their intersections were calculated to describe the interrelationship between them. The results showed that the generalized dimensions of intersections in different brain states decreased according to the following order: rest with eyes open, closed, light sleep, and deep sleep. The generalized dimensions of intersections related to the left or right temporal lobe were higher than the others when the subjects was doing mental arithmetic, and there was a decrease when the subjects listened to soft classical music. In addition, it was found that there was a noticeable difference in singular spectra between epileptic patients and normal subjects, irrespective of whether the epileptic patient was experiencing a seizure or not. Received: 3 July 2000 / Accepted in revised form: 30 October 2000     

A measure for the angle between projections based on the extent of correlation between corresponding central sections

A pre-condition for the ab initio assignment of Euler angles to a set of projections from an asymmetric object is that at least three of the available projections correspond to rotations about different axes. For symmetric objects this condition may be relaxed. There are some applications of single-particle electron microscopy, such as the reconstruction of filamentous macromolecular assemblies, where all available projections more-or-less correspond to rotations about a common rotation axis making it difficult to satisfy this condition. Here, a method has been developed to overcome this problem, based on the fact that the correlation between two central sections of the Fourier transform of a compact object will not be limited to an infinitesimal central line but will have a finite extent, which is related to the angle between the corresponding projections. Projections from model filaments, with different degrees of rotational symmetry about the long axis, have been used to test the methodology. The results show that angle determination is robust down to signal-to-noise ratios as low as 2 and that, in general, the error decreases as the degree of symmetry increases. The method has been used to assign angles to a set of negatively stained muscle thick filament projections to obtain an initial 3D reconstruction. The main features of the projections are seen to be faithfully reproduced in the reprojections from the reconstruction. A real-space adaptation of this method is also discussed.