Fundamental Structural Elements Research Articles

Molecular mechanisms for proton transport in membranes.

Likely mechanisms for proton transport through biomembranes are explored. The fundamental structural element is assumed to be continuous chains of hydrogen bonds formed from the protein side groups, and a molecular example is presented. From studies in ice, such chains are predicted to have low impedance and can function as proton wires. In addition, conformational changes in the protein may be linked to the proton conduction. If this possibility is allowed, a simple proton pump can be described that can be reversed into a molecular motor driven by an electrochemical potential across the membrane.

The Nuclear Protein Matrix: Isolation, Structure, And Functions

A new structure has been isolated from mammalian nuclei and characterized, and has been termed the nuclear protein matrix. It appears that this fundamental structural element is involved in the regulation of both nuclear function and form.

D-glyceraldehyde-3-phosphate dehydrogenase: three-dimensional structure and evolutionary significance.

A 3.0-A resolution electron density map of lobster glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12) was computed. The essentially single isomorphous replacement map was very substantially improved by averaging subunits. NAD binds in an open conformation at sites close to subunit interfaces. The coenzyme binding portion of the enzyme has almost the same fold as the corresponding portion of lactate dehydrogenase (EC 1.1.1.27). The presence of this structure in the five enzymes, analyzed so far, that use nucleotide coenzymes might indicate a fundamental primordial structural element.

On a Simplified Method for Solving Impulsively Loaded Structures of Rate-Sensitive Materials

In an attempt to assess more completely rate-sensitive material effects, two fundamental structural elements are analyzed: A wire with an impulsively loaded end mass, and an impulsively loaded ring. The ring and wire are made of perfectly plastic, rate-sensitive materials. In each case, exact and approximate solutions are obtained for an exponential rate-sensitivity law. The results suggest that very good approximations to the exact solutions may be found by utilizing a rate-insensitive material with constant yield stress equal to the initial dynamic yield stress.

Cell Structures and Their Significance for Ameboid Movement

Publisher Summary This chapter explains how modern cell morphology, which is largely based on electron microscopy, can contribute to the analysis of the mechanism of ameboid movement. In order to correlate structure and dynamics with reference to the mechanism of ameboid movement it is necessary also to consider the dynamics of certain fundamental structural elements of the cell, for instance, the important cytoplasmic membranes. This requires, furthermore, the discussion of certain morphogenetic principles which are essential to an understanding of the dynamics of the cell ultrastructures. The close connection between the dynamics of individual structural components, their morphogenetic capacities, and the phenomenon of protoplasmic motility is due to the fact that in the macromolecular region of living matter, dynamics, morphogenesis, and motility cannot be treated separately because these are largely interdependent or identical. Ameboid movement is the motion mechanism by means of which not only protozoa and blood cells but also tissue cells and most embryonic cells propel themselves or accomplish certain metabolic functions. An analysis of the mechanism of ameboid movement is therefore of obvious importance, and is discussed in the chapter.