Biomolecules optically active

Another hypothesis on homochirality involves interaction of biomolecules with minerals, either at rock surfaces or at the sea bottom thus, adsorption processes of biomolecules at chiral mineral surfaces have been studied. Klabunovskii and Thiemann (2000) used a large selection of analytical data, provided by other authors, to study whether natural, optically active quartz could have played a role in the emergence of optical activity on the primeval Earth. Some researchers consider it possible that enantioselective adsorption by one of the quartz species (L or D) could have led to the homochirality of biomolecules. Asymmetric adsorption at enantiomor-phic quartz crystals has been detected L-quartz preferentially adsorbs L-alanine. Asymmetrical hydrogenation using d- or L-quartz as active catalysts is also possible. However, if the information in a large number of publications is averaged out, as Klabunovskii and Thiemann could show, there is no clear preference in nature for one of the two enantiomorphic quartz structures. It is possible that rhomobohedral... 

Ever since the beginning of life on primitive Earth, biopolymers and biomolecules have essentially comprised optically active constituents because of the natural selection of Z-amino acids and tZ-sugars. Although the origin of this biomolecular handedness is a long debated issue among biologists, chemists, physicists, and astronomers,1 5 it is accepted that our life is a consequence of the chemistry of homochiral biosubstances. Deoxyribonucleic acid (DNA) is a classic example of a chiral biopolymer. Its chirality is essentially characterized... 

With respect to an enzyme, the rate of substrate-to-product conversion catalyzed by an enzyme under a given set of conditions, either measured by the amount of substance (e.g., micromoles) converted per unit time or by concentration change (e.g., millimolarity) per unit time. See Specific Activity Turnover Number. 2. Referring to the measure of a property of a biomolecule, pharmaceutical, procedure, eta, with respect to the response that substance or procedure produces. 3. See Optical Activity. 4. The amount of radioactive substance (or number of atoms) that disintegrates per unit time. See Specific Activity. 5. A unitless thermodynamic parameter which is used in place of concentration to correct for nonideality of gases or of solutions. The absolute activity of a substance B, symbolized by Ab, is related to the chemical potential of B (symbolized by /jlb) by the relationship yu,B = RTln Ab where R is the universal gas constant and Tis the absolute temperature. The ratio of the absolute activity of some substance B to some absolute activity for some reference state, A , is referred to as the relative activity (usually simply called activity ). The relative activity is symbolized by a and is defined by the relationship b = Ab/A = If... 

There are many systems of different complexity ranging from diatomics to biomolecules (the sodium dimer, oxazine dye molecules, the reaction center of purple bacteria, the photoactive yellow protein, etc.) for which coherent oscillatory responses have been observed in the time and frequency gated (TFG) spontaneous emission (SE) spectra (see, e.g., [1] and references therein). In most cases, these oscillations are characterized by a single well-defined vibrational frequency, It is therefore logical to anticipate that a single optically active mode is responsible for these features, so that the description in terms of few-electronic-states-single-vibrational-mode system Hamiltonian may be appropriate. 

Chiral compounds are very important substances. Many natural products, medicinal compounds, and biomolecules exist as a single, optically active stereoisomer. Furthermore the opposite enantiomer or diastereomer may not have any physiological activity or may, in fact, have a detrimental physiological effect. There is therefore great interest in reactions in which only one stereoisomeric form of a compound is produced by a particular synthetic sequence. 

First measurements for identifying optical activity in Raman scattering were undertaken soon after the Raman effect itself was discovered but proved unsuccessful [1,2]. The fact that the measurement of solutions of biomolecules is at present the most important application of ROA is remarkable in the face of the experimental difficulties which haunted these early attempts to observe it, even for pure, chiral liquids, the most favorable experimental situation. 

Chiral conjugate polymers such as polythiophenes with an optically active substituent in the 3 position have been studied for use in optoelectronic devices, sensors, and catalysis (Nilsson et al., 2004). These materials show activity based on their chiral behaviors, which can be influenced by solvent or temperature. Flelical biomolecules can be used to induce chirality in optically inactive polythiophenes (Ewbank et al., 2001). Nilsson et al. (2004) extended this to use a positively charged random-coil peptide conjugated with a... 

Determination of the Structure of a Biomolecule An unknown substance, X, was isolated from rabbit muscle. Its structure was determined from the following observations and experiments. Qualitative analysis showed that X was composed entirely of C, H, and O. A weighed sample of X was completely oxidized, and the H20 and C02 produced were measured this quantitative analysis revealed that X contained 40.00% C, 6.71% H, and 53.29% O by weight. The molecular mass of X, determined by mass spectrometry, was 90.00 u (atomic mass units see Box 1-1). Infrared spectroscopy showed that X contained one double bond. X dissolved readily in water to give an acidic solution the solution demonstrated optical activity when tested in a polarimeter. 

Dukor RK, Nafie LA (2000) Vibrational optical activity of pharmaceuticals and biomolecules. In Meyers RA (ed) Encyclopaedia of analytical chemistry instrumentation and applications. Wiley, Chichester, UK, pp 662-676... 

Barron LD. Structure and behaviour of biomolecules from Raman optical activity. Curr. Opin. Struct. Biol. 2006 16 638-643. Wuthrich K. NMR studies of structure and function of biological macromolecules (Nobel Lecture). J. Biomolec. NMR 2003 27 13-39. 

In this context, it is fascinating that 18 of the natural amino acids crystallize as racemates in a ratio of 1 1, except for threonine and arginine that crystallize as pure d- and pure L-crystals. Serine is particularly unusual as it is formed with an ee of 99% starting from an initial racemate in aqueous solution (Klussmann et al. 2006). Putting the data into perspective, one may conclude that it was likely that meteoritic impact delivered defined molecules from space to Earth. Among them, stereoisomers of a-methyl amino acids were in ee. These optically active compounds were the starting material for the transfer of chirality to other biomolecules. This... 

The formation of enantiopure optically active biomolecules is an important chapter in the history of evolution. The physical phenomena which can generate and augment asymmetry... 

Quartz and other minerals, e.g., clays, have chiral sites on the surface. It was attempted to separate chiral compounds selectively. A very small chiral selection effect by clay minerals was reported. It was argued that the chiral sites of these minerals would arise from the adsorption of optically active biomolecules. This means that prebiotic clays would then have had no chiral sites. 

Semiconductor nanopartides are of particular importance due to their optical properties. They act as quantum dots and can be applied as components in optically active materials, as optically active labels for biomolecules and cells and as components in miniaturized optoelectronic devices [16]. Compound semiconductor nanopartides can be prepared by liquid-phase processes. Several groups have investigated the preparation of CdSe partides. The fluorescence emission of these particles is strongly dependent on the particle size. The realization of well[Pg.783]

Vibrational Raman optical activity of biomolecules, including carbohydrates, has been reviewed (23 refs). l A general procedure for assigning both relative and absolute configuration to multiple stereocentres in acyclic aminopolyols based on application of the exiton chirality method is presented. The method has been applied to the side chain aminopolyol of a natural bacterial-derived terpenoid derivative. ... 

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