G. Gilat | Searcharxiv

arXiv2002

Physical Chirality. It Feeds on Negative Entropy

Chirality is considered by many scientists to be mainly a geometric concept. There exists also a physical aspect of chirality which is largely being overlooked at. Two examples of mechanical devices are introduced here that represent ``Physical Chirality''. These are a rotating water sprinkler and a variant of Crookes' radiometer. When interacting with appropriate media, they both choose only one mode of rotation out of two possible ones. Such a behavior does not obey time-reversal invariance, which is regarded to be a rule in classical mechanics. This is due to their chiral nature. Instead, they do obey a space-time (ST) law of invariance, that is, what is rotating in the opposite direction is the mirror-image of the given device. In a recent experiment of Koumura et al. they discovered a similar behavior of a molecular rotor. The possible biological significance of physical chirality is emphasized hereby, and the conclusion is that chiral molecular systems do not reach readily thermal equilibrium. In other words: ``Physical chirality does feed on negative entropy'', and therefore, it may well be of crucial value to life.

physics.bio-ph↗

arXiv1999

On the Biological Advantage of Chirality

The presence of chirality in the main molecules of life may well be not just a structural artifact, but of pure biological advantage. The possibility of the existence of a phenomenon of a special mode of interaction, labeled as "chiral interaction" (CI), for which structural chirality is a necessary condition, is the main reason for such an advantage. In order to demonstrate such a possibility, macroscopic chiral devices are introduced and presented as analogies for such an interaction. For this purpose it is important to make a clear distinction between geometric and physical chiralities, where the latter are capable to perform chiral interactions with various media. Apart from chirality, a few other structural elements are required. In particular, the presence of an interface that separates between the chiral device and the medium with which it is interacting. The physical chirality is build into this very interface where chiral interaction is taking place. On a molecular level, soluble proteins in particular, the active medium is the presence of random ionic motion in the aqueous solvent. As a result of chiral interaction a certain perturbation, or current, is generated and flowing along the coils of $ α$-helix structure in one preferred direction out of two possible ones. A model for such a chiral interaction is presented and a few significant consequences are pointed out. In particular, it is important to emphasize the time-irreversible feature of chiral interaction, which leads to its non-ergodic nature that is to be considered a necessary condition for evolutionary processes in biomolecules. There exists an experimental result by Careri et al. who found a clear linkage between the free protonic motion in the hydration layer of protein s and their enzymatic activity.

physics.bio-ph↗