Clays in prebiological chemistry

Summary In this review an attempt is made to highlight the structures and properties of clay that may contribute to a better understanding of the role of clays in chemical evolution. The adsorption of organic molecules on clays has been demonstrated, as has the synthesis of bioorganic monomers in the presence of clays. For instance, amino acids (glycine, aspartic acid, threonine, alanine and others) as well as purines and pyrimidines, have been obtained from CO and NH₃ in the presence of clays at relatively high temperatures (250-325°C). Carbohydrates are also easily derived from formaldehyde at relatively low temperatures (80°C). The oligomerization of biochemical monomers, mediated by clays has also been shown to result in the formation of polymer molecules basic to life. For instance the condensation of amino acyl adenylates at room temperature in the presence of montmorillonite is known to yield polypeptides in discrete ranges of molecular weights with degrees of polymerization up to 56. Clays have also been found to affect the condensation of mononucleotides to oligonucleotides. Although the role of clays in the origin of metabolic pathways has not been demonstrated, it is possible that clays may have played a cooperative role with catalytic peptides in an intermediate stage of prebiological chemistry preceding the emergence of life on this planet.     

On the non-existence of eloxanthin

Abandonment of the name eloxanthin is proposed. The principal carotenoids in various species of Elodea were (3R, 3′R, 6′R)-lutein (β,ε-carotene-3, 3′-diol) and β, β-carotene. The minor pigments were neoxanthin-X (5′, 6′-epoxy-6, 7-didehydro-5, 6, 5′, 6′-tetrahydro-β, β-carotene-3, 5, 3′-triol), 9′-cis-neoxanthin- X, 9- and 13-cis-violaxanthin (5, 6, 5′, 6′-diepoxy-5, 6, 5′, 6′-tetrahydro-β, β-carotene-3, 3′-diol), antheraxanthin (5, 6-epoxy-5, 6-dihydro-β, β-carotene-3, 3′-diol), neolutein A (13- or 13′-cis-lutein) and neolutein B (9- or 9′-cis-lutein). All attempts to isolate eloxanthin failed.     

Cytogenetic and electrophoretic evidence for a polyploid origin of the basic chromosome number x = 14 in the genusAsphodelus (Liliaceae)

Cytogenetic and electrophoretic analyses on 2n = 28 strains ofAsphodelus cerasiferus strongly suggest that the basic number x = 14 of the genusAsphodelus is of secondary polyploid origin from x = 7.     

Microfluorometric filter determination of DNA in sucrose density gradients

A simple filter method for the fluorometric estimation of DNA in alkaline and neutral sucrose gradient fractions with DABA·2HCl is discussed. Alpha-450 membrane filters of regenerated cellulose (Gelman Instrument Co., Ann Arbor, Michigan) were used. In the proposed method washing of the DNA precipitate as well as the reaction with DABA·2HCl were performed directly on the filters, thus avoiding repeated washing and centrifugations of DNA precipitates applied hitherto in analogous fluorometric techniques. A good coincidence of the results concerning localization of DNA sedimentation profiles determined by radioisotopic and fluorometric methods was obtained. The method is very convenient for DNA estimation in alkaline and neutral sucrose density gradient fractions obtained by ultracentrifugation of DNA of nonproliferating cells where DNA labeling is very difficult, and in the case of human lymphocytes even impossible without stimulation for blastic transformation. Its other advantages are a considerably simplified procedure and a higher precision with respect to other fluorometric methods for determination of DNA.     

Protein-lipid interactions. A nuclear magnetic resonance study of sarcoplasmic reticulum Ca2,Mg2+-ATPase, lipophilin, and proteolipid apoprotein-lecithin systems and a comparison with the effects of cholesterol.

Deuterium Fourier transform nuclear magnetic resonance (NMR) spectra at 34 MHz (corresponding to a magnetic field strength of 5.2 T) have been obtained of a variety of protein-lipid systems containing specifically deuterated phospholipids. The following systems were investigated as a function of temperature: sarcoplasmic reticulum ATPase (ATP phosphohydrolase, EC 3.6.1.3) complexed with 1-myristoyl-2-(14,14,14-trideuteriomyristoyl)-sn-glycero-3-phosphocholine (DMPC-d3) or 1,2-bis(16,16,16-trideuteriopalmitoyl)-sn-glycero-3-phosphocholine (DPPC-k6); human brain lipophilin complexed with DPPC-d6 or 1,2-bis(6,6-dideuteriopalmitoyl)-sn-glycero-3-phosphocholine (DPPC-6,6-d4); beef brain myelin proteolipid apoprotein (PLA) reconstituted with DMPC labeled as CD2 (or CD3) at one or more of positions 3, 4, 6, 8, 10, 12, or 14 of the sn-2 chain. For purposes of comparison, spectra were also obtained for bilayers containing cholesterol (CHOL). The results show that proteins either disorder or have little effect on hydrocarbon chain order in membranes above the gel to liquid-crystal phase transition temperature (Tc) of the pure lipids. Cholesterol, however, causes a very large ordering of the hydrocarbon chains above Tc, but both cholesterol and protein prevent chain crystallization (by effectively disordering chain packing) immediately below Tc. No evidence for any ordered "boundary lipid" in association with protein was found above Tc, perhaps due to the rough nature of protein surfaces. Above Tc, exchange between free bilayer and protein associated lipid is fast on the time scale of the deuterium NMR experiment (greater than or similar to 10(3) s-1). We have also obtained proton-decoupled phosphorus-31 nuclear magnetic resonance spectra at 60.7 MHz (corresponding to a magnetic field strength of 3.5 T) of DMPC, DMPC-AT-Pase, and DMPC-CHOL complexes. The results indicate that ATPase and CHOL CAUSE SMALL DECREASES IN 31P chemical shielding anisotropies but that in addition ATPase causes a four- to fivefold increase in 31P spin-lattice and Carr-Purcell spin-spin relaxation rates, suggesting the possibility of polar group protein-lipid interaction leading to increased correlation times in the region of the lipid phosphate head group.