Crystallization and preliminary X-ray studies of hydroxylamine oxidoreductase from Nitrosomonas europaea.

Hydroxylamine oxidoreductase [EC 1.7.3.4] from Nitrosomonas europaea was crystallized by the microdialysis method using ammonium sulfate. Its space group is P63 with cell dimensions of a = b = 96.4 A and c = 266.2 A. Its molecular weight was determined to be 190,000-195,000 by the X-ray small angle scattering and ultracentrifugal methods.

Biomechanical effect of anteriorly directed extraoral forces on the craniofacial complex: a study using the finite element method.

This study was designed to investigate the biomechanical effect of protractive maxillary orthopedic forces on the craniofacial complex by use of the three-dimensional finite element method (FEM). The three-dimensional FEM model was developed on the basis of a dry skull of a young human being. The model consisted of 2918 nodes and 1776 solid elements. Eighteen cranial and facial sutural systems were integrated in the model. An anteriorly directed 1.0-kg force was applied on the buccal surfaces of the maxillary first molars in both a horizontal parallel direction and a 30 degree obliquely downward direction to the functional occlusal plane. The nasomaxillary complex showed a forward displacement with upward and forward rotation in a horizontal protraction case, whereas a downward force produced almost translatory repositioning of the complex in an anterior direction. High stress levels were observed in the nasomaxillary complex and its surrounding structures. However, the pattern of stress distributions within the complex was different in two force systems. A downward protraction force produced relatively uniform stress distributions, indicating the importance of the force direction in determining the stress distributions from various orthopedic forces.

Preliminary X-ray studies on Serratia protease.

Preliminary X-ray studies on Serratia protease have been carried out using crystallographic and small angle scattering techniques. The enzyme has been crystallized in three different crystalline forms by microdialysis and vapor diffusion methods using 50 mM phosphate buffer, pH 6.0, at 24 degrees C. They have orthorhombic space groups: C222(1) for one form and P2(1)2(1)2(1) for the other two forms. A small angle X-ray scattering study showed that the radius of gyration and the maximal dimension of the molecule in aqueous solution are 26.6 A and 94.5 A, respectively. The molecular weight of the enzyme was determined to be 45,000-48,000 by various physical methods.

Formation of a complex between yeast L-lactate dehydrogenase (cytochrome b2) and cytochrome c. Ultracentrifugal and gel chromatographic analyses.

Yeast L-lactate dehydrogenase formed a stable complex with cytochrome c in weakly alkaline solution of low ionic strength. The binding ratio of cytochrome c to the enzyme depended on whether free cytochrome c was present: In the presence of a micromolar concentration of cytochrome c the enzyme formed a complex with about two molecules of cytochrome c, whereas the enzyme was in a 1:1 molecular complex after removal of free cytochrome c. This suggests that the binding of one molecule of cytochrome c changes the affinity of the other binding site on the enzyme for cytochrome c. The enzyme consists of four presumably identical subunits, each containing a binding site for cytochrome c. Thus, present data confirm the concept of negative cooperativity between the subunits of the enzyme molecule in their interaction with cytochrome c.