Chiral Objects Research Articles

Chiral interaction in protein structures

A new mode of interaction, to be termed “chiral interaction”, is proposed between chiral molecules such as proteins and polar solvents (H2O). Such a mode of interaction is well-recognized for macroscopic chiral devices, such as windmills or electric cells, and various media, such as wind or electrolyte. This mode of interaction requires several structural ingredients, all possessed by proteins, and its source is in ionic motion in the solvent. Such an interaction exists only for chiral objects or molecules and therefore possesses several peculiar and uncommon features, which may be of special biological significance. From a thermodynamical viewpoint this phenomenon is non-ergodic and time-irreversible, and therefore does not obey the principle of detailed balance. The energy content of this interaction is rather small and therefore it is to be regarded as a subthermal organization. Chiral interaction appears in the form of an intrinsic flow of perturbation or currents throughout the molecule and hence it is not easily observable. Two experiments are proposed for its observation. One is direct and the other is based on an assumption that couples chiral interaction with enzymatic activity. A model is proposed that links this interaction with the natural selection of the L-enantiomer of amino acids via the magnetic field of the earth. Several structural and other properties may obtain biological significance via the concept of chiral interaction. It is conjectured that chiral interaction may play a significant role in the control of protein activity.

On the quantification of asymmetry in nature

A new concept of quantitative measure of the amount of structural asymmetry is introduced and defined by maximal overlap between two enantiomers of the same chiral body. This concept is to be called chiral coefficient, and it can readily be extended to physical properties such as mass or electronic wave-function distributions over chiral objects such as molecules or unit cells in crystals. The mathematical aspects of these coefficients are discussed. There exist two cases of maximal overlaps, symmetric and asymmetric, where for the asymmetric case there exist two positions of maximal overlap. It is also shown that there always exists a natural directionz for every asymmetric body for any physical property treated. The possibility of quantizing structural asymmetry is discussed, and, if it exists, it may be associated with the naturalz axis of the chiral system. Possible applications of asymmetry quantification are discussed.

Electromagnetic chirality and its applications

Chirality is a geometric notion which refers to the handedness of an object. A chiral object is, by definition, a body that cannot be brought into congruence with its mirror image by translation and rotation. In other words, such a body lacks bilateral symmetry, and cannot be superposed on its mirror image. An object of this sort has the property of handedness and is said to be either right-handed or left-handed. An object that is not chiral is achiral. Some chiral objects occur in two versions relatedto each other as a chiral object and its mirror image. Objects so related are said to be enanriomorphs of each other. If a chiral object is found to be lefthanded, its enantiomorph is right-handed, and vice versa. Two examples of chiral objects, the Mbbius strip and the irregular tetrahedron, and their enantiomorphs are shown in Fig. 1. Note that these objects and their mirror images are incongruent

On a fourth-order wave equation for EM propagation in chiral media

A fourth-order wave equation is derived to study the propagation of an electromagnetic (EM) wave in a medium composed of chiral objects. This approximate wave equation does not reflect the handedness of the medium directly, which is more readily apparent, however, in a pair of two coupled second-order wave equations obtaineden route.

Differential Absorption and Differential Scattering of Circularly Polarized Light: Applications to Biological Macromolecules

A chiral object is defined as an object that is not superimposable on its mirror image. (The group theoretical definition of a chiral object is one that has no rotation-reflection symmetry axes, Sn). Chiral objects can interact differently with left arid right circularly polarized light. Therefore, it is of interest to study this interaction and to learn how this chiral interaction differs from the interaction with unpolarized, or linearly polarized, light. Our emphasis is on chiral molecules, such as proteins, nucleic acids, and viruses. Large here means relative to the wavelength of light, but as circularly polarized X-radiation becomes available in synchrotron sources (1 , 2), large will include any molecule.

Optical activity and time reversal

The role of time reversal symmetry in natural and magnetic optical activity is discussed. Natural optical rotation is shown to be generated by an anti-hermitian odd parity time-even operator and magnetic optical rotation by an anti-hermitian even parity time-odd operator. This shows that lack of time reversal invariance is not the source of natural optical rotation and that free atoms can show natural optical rotation without violating reversality, which leads to a fundamental distinction between the conditions necessary for natural optical rotation and a permanent space-fixed electric dipole moment. General transition optical activity and polarizability tensors between components of degenerate states are discussed with reference to possible new Raman experiments and new contributions to discriminating intermolecular forces between chiral molecules. Time reversal symmetry also leads to a new criterion for chiral objects and to the concept that natural optical activity provides an example of spontaneous sy...

On electromagnetic waves in chiral media

We analyze the propagation of electromagnetic waves through chiral media, i.e., through composite media consisting of macroscopic chiral objects randomly embedded in a dielectric. The peculiar effects that such media have on the polarization properties of the waves are placed in evidence. To demonstrate the physical basis of these effects, a specific example, chosen for its analytical simplicity, is worked out from first principles.

A simple dynamic stereomodel for the interconversion of enantiomers via a high-energy achiral intermediate

A simple dynamic stereomodel for the interconversion of enantiomers via a high-energy achiral intermediate because introduction of molecular chirality to the elementary students is often effectively made by the comparison of familiar chiral and achiral objects.