Biomedical subjects
Publications and source records attributed to J L Bada.
Reduction of C60 with rhodium(0) on alumina and hydrogen in deuterated benzene (C6D6) at ambient temperature and pressure yields a mixture of hydrogenated compounds; C60H2 has been characterized as the major product in 14% yield based on 1H NMR.
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We have analyzed the H4 ordinary chondrite Forest Vale for polycyclic aromatic hydrocarbons (PAHs) using two-step laser mass spectrometry (L2MS) and for amino acids using a standard chromatographic method. Indigenous PAHs were identified in the matrices of freshly cleaved interior faces but could not be detected in pulverized silicates and chondrules. No depth dependence of the PAHs was found in a chipped interior piece. Amino acids, taken from the entire sample, consisted of protein amino acids that were nonracemic, indicating that they are terrestrial contaminants. The presence of indigenous PAHs and absence of indigenous amino acids provides support for the contention that different processes and environments contributed to the synthesis of the organic matter in the solar system.
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1. The blue-green coloration of the blood plasma in some marine fishes, which is attributed to a protein bound tetrapyrrol (biliverdin), is an anomaly in vertebrates. 2. Recent studies have shown that biliverdin not only occurs in many fish, but is also present in the blood of tobacco hornworm, the wings of moth and butterfly, the shell of bird eggs, the serum and egg of frog, the placenta of dog and in the blood of humans suffering from hepatic diseases. 3. In this review, we begin with a historical account of the description of the presence of blue-green blood plasma in fish, and then consider the biochemistry, metabolism, physiology, and the ecological implications of biliverdin in fish. 4. A comparative description of the occurrence of biliverdin in fish and other animals is presented. 5. The mechanism of accumulation of biliverdin in fish blood and its evolutionary significance are also considered. It is suggested that this process may serve as a useful model for further research on bile pigment metabolism in other animals.
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Since the discovery nearly a decade ago that Cretaceous/Tertiary (K/T) boundary layers are greatly enriched in iridium, a rare element in the Earth's crust, there has been intense controversy on the relationship between this Ir anomaly and the massive extinction of organisms ranging from dinosaurs to marine plankton that characterizes the K/T boundary. Convincing evidence suggests that both the Ir spike and the extinction event were caused by the collision of a large bolide (greater than 10 km in diameter) with the Earth. Alternative explanations claim that extensive, violent volcanism can account for the Ir, and that other independent causes were responsible for the mass extinctions. We surmise that the collision of a massive extraterrestrial object with the Earth may have produced a unique organic chemical signature because certain meteorites, and probably comets, contain organic compounds which are either rare or non-existent on the Earth. In contrast, no organic compounds would be expected to be associated with volcanic processes. Here we find that K/T boundary sediments at Stevns Klint, Denmark, contain both alpha-amino-isobutyric acid [AIB,(CH3)2CNH2COOH] and racemic isovaline [ISOVAL, CH3CH2(CH3)CNH2COOH], two amino acids that are exceedingly rare on the Earth but which are major amino acids in carbonaceous chondrites. An extraterrestrial source is the most reasonable explanation for the presence of these amino acids.
The discovery of hydrothermal vents at oceanic ridge crests and the appreciation of their importance in the element balance of the oceans is one of the main recent advances in marine geochemistry. It is likely that vents were present in the oceans of the primitive Earth because the process of hydrothermal circulation probably began early in the Earth's history. Here we examine the popular hypothesis that life arose in these vents. This proposal, however, is based on a number of misunderstandings concerning the organic chemistry involved. An example is the suggestion that organic compounds were destroyed on the surface of the early Earth by the impact of asteroids and comets, but at the same time assuming that organic syntheses can occur in hydrothermal vents. The high temperatures in the vents would not allow synthesis of organic compounds, but would decompose them, unless the exposure time at vent temperatures was short. Even if the essential organic molecules were available in the hot hydrothermal waters, the subsequent steps of polymerization and the conversion of these polymers into the first organisms would not occur as the vent waters were quenched to the colder temperatures of the primitive oceans.
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The organic compounds synthesized in prebiotic experiments are racemic mixtures. A number of proposals have been offered to explain how asymmetric organic compounds formed on the Earth before life arose, with the influence of chiral weak nuclear interactions being the most frequent proposal. This and other proposed asymmetric syntheses give only sight enantiomeric excess and any slight excess will be degraded by racemization. This applies particularly to amino acids where half-lives of 10(5)-10(6) years are to be expected at temperatures characteristic of the Earth's surface. Since the generation of chiral molecules could not have been a significant process under geological conditions, the origins of this asymmetry must have occurred at the time of the origin of life or shortly thereafter. It is possible that the compounds in the first living organisms were prochiral rather than chiral; this is unlikely for amino acids, but it is possible for the monomers of RNA-like molecules.
The general principals of the amino acid racemization based dating technique are discussed. The results obtained at Olduvai Gorge (Tanzania) and Zhoukoudian (China) are presented as an illustration of the paleoanthropological application of racemization dating. Tooth enamel provides the best material for the racemization dating of Middle to Lower Pleistocene deposits, although in some cases bones also yield reliable ages. The racemization method provides a means of dating teeth and bones which are too old for radiocarbon dating. Only small samples are required and processing procedures are straightforward. The technique is particularly useful in paleoanthropological studies since hominid fossils can be directly dated.
During the period of June to October 1985, a study in vivo was made on 162 patients suffering from malaria by P. falciparum, in order to evaluate the sensitivity of the parasite to the drugs: Chloroquine, Amodiaquine and Pyrimethamine-Sulfadoxine (Fansidar). As an alternative treatment, in the resistant cases, Quinine with Fansidar or Quinine with Tetracycline was given. The following cases of resistance were found: 17 cases to Chloroquine (5-RI, 9-RII, 3-RIII), 7 cases to Amodiaquine (5-RI, 2-RII) and 2 cases to Fansidar (1-RI, 1-RII). It is recommended that the epidemiologic studies of the resistance by P. falciparum to the anti-malarials be increased, following up the evolution of its scope, and the organization of a program to fight against malaria. Also the use of Fansidar is recommended as the principal medicine against P. falciparum in malaria without complications, in the zones where there is strong resistance to the 4-amino-quinoleines. In case of multi-resistance in malaria by P. falciparum, the use of Quinine is recommended. At a prophylactic level we do not advise the use of Chloroquine as the only medicine, nor the use of Fansidar because of its potential toxic effects.