Heterogeneous and epitaxial nucleation of protein crystals on mineral surfaces     

McPherson A  Shlichta P 《Science (New York, N.Y.)》1988,239(4838):385-387

Fifty different mineral samples were tested as potential heterogeneous or epitaxial nucleants for four commonly crystallized proteins. It was found, by conventional protein crystallization techniques, that for each protein there was a set of mineral substrates that promoted nucleation of crystals at lower critical levels of supersaturation than required for spontaneous growth. Numerous examples, involving all four proteins, were observed of modification of crystal habit and, in some cases, unit cell properties promoted by the presence of the mineral nucleants. In at least one case, the growth of lysozyme on the mineral apophyllite, it was shown by lattice analysis and x-ray diffraction that the nucleation and growth of the protein crystal on the mineral was likely to involve a direct lattice match.  相似文献   

Shattered stars: supernova remnants and the interstellar medium     

Murdin P 《Science (New York, N.Y.)》1988,241(4861):105-106

  相似文献   

Soviet science     

Abelson PH 《Science (New York, N.Y.)》1988,239(4843):961

  相似文献   

Response: icosahedral symmetry     

Steinhardt PJ 《Science (New York, N.Y.)》1988,239(4843):963-964

  相似文献   

Einstein in his youth: the collected papers of albert einstein     

Loewenberg P 《Science (New York, N.Y.)》1988,239(4839):510-512

  相似文献   

Improving u.s. Capabilities in technology     

Abelson PH 《Science (New York, N.Y.)》1988,242(4878):493

  相似文献   

Dynamic properties of molecularly thin liquid films     

Israelachvili JN  McGuiggan PM  Homola AM 《Science (New York, N.Y.)》1988,240(4849):189-191

An experimental technique is described for simultaneously measuring the static and dynamic interactions of very thin liquid films between two surfaces as they are moved normally or laterally relative to each other. Film thickness can be measured and controlled to 1 angstrom. Initial results are presented of the transition in the physical properties of liquid films only one molecular layer thick to thicker films whose properties are practically indistinguishable from the bulk. In particular, the results show that two molecularly smooth surfaces, when close together in simple liquids, slide (shear) past each other while separated by a discrete number of molecular layers, and that the frictional force is "quantized" with the number of layers.  相似文献   

Outside Views of Science: Science under Scrutiny     

Durbin PT 《Science (New York, N.Y.)》1984,224(4652):984

  相似文献   

Book reviews     

C. Fisher  A. B. Gilbert 《British poultry science》1984,25(2):294-295

The T.M.E. System of Feed Evaluation. I.R. Sibbald, Animal Research Centre Contribution 83‐1, Animal Research Centre, Ottawa, Ontario, Canada.

Physiology and Behaviour of the Pigeon, edited by M. Abs. 1983. 360 pages, illustrated. London, Academic Press Ltd. Price £34.00. ISBN 0 12 042950 0.  相似文献   

A mathematical representation of the Ovulatory cycle of the domestic hen     

R.J. Etches  J.P. Schoch 《British poultry science》1984,25(1):65-76

1. The ovulatory cycle of the domestic hen (Gallus domesticus) was postulated to be the result of the interaction of two independent systems.

2. A circadian system was postulated to control the restriction of ovulation to an 8‐h period of the day under conventional 14 h light: 10 h dark regimes.

3. The final phase of follicular maturation was postulated to commence after ovulation of the preceding ovum in the hierarchy.

4. Ovulation was postulated to occur when a mature follicle was present in the ovary during the appropriate phase of the circadian‐linked system.

5. The predicted times of oviposition were within the standard error of the observed times of oviposition under 21‐, 24‐ and 28‐h photoschedules.

6. It was concluded that this hypothesis for the control of the ovulatory cycle of the hen is consistent with current knowledge.  相似文献