Biogenic structures

A biogenic structure in ALH84001 is 100 nm long and 25 nm in diameter. Assume that the structure is a cylinder and calculate the internal volume in zeptolitres (zl). 

Biogenic structures Structures in fossils or rock formations that may have been formed by biological activity. 

Biogenic Structure Product OH reaction yield Oj reaction yield... 

Schternberg, L.E., 1967. Biogenic structures in manganese ores. Microbiology, 36 710— 712. 

In addition to this published data we identified several non-halogenated contaminants, which are also specific for this local emission due to their obviously non-biogenic structures and the point source related spatial distribution. In detail, 4-nitrobenzoic acid [ 1] was only detected at sampling locations T1 and T2 situated nearby the industrial point source (see Table 4). Also in samples T1 and T2 the concentrations of 4-ethylnitrobenzene [ 2], formylpiperidine [ 3] and acetylpiperidine [ 4] increased significantly up to 61, 39 and 28 ng/g, respectively (see Table 3), compared to stations T5 and T6, which are assumed to be contaminated only by diffuse sources, representing therefore background samples with respect to the industrial point source. 

Fig. 5. Parts of two vertically oriented x radiographs taken at FOAM. A massive shell layer of varied thickness (6-8 cm) overlies a well-laminated zone in both cases. There is relatively little evidence of biogenic structures although burrows can be made out in the shell layer. Beneath the laminated zone are additional shell layers down to at least SO cm. (Scale 3 cm.)...

Spider venom peptides, toxic peptides from spiders that mainly modulate neurotransmission. Spider venoms are rich in neurotoxins that influence ion channels, interfere with neurotransmitter exocytosis, or affect neurotransmitter binding. The most important families are the atracotoxins (36-68 amino acids) and the latrotoxins. Many spider venom peptides are translated as prepropeptides and post-translationally modified, e.g., by disulfide bridge formation and C- or N-terminal modification. Because of the high diversity of its constituents, the spider venom is sometimes regarded as a biogenic structurally constrained combinatorial peptide library where nearly all amino acids of the mature sequence may be mutated, with the exception of a few strictly conserved cysteine residues responsible for the three-dimensional fold of the toxin [G. Estrada etal, Nat. Prod. Rep. 2007, 24,145]. 

S. Maim and C. C. Perry, Structural Aspects of Biogenic Silica, Ciba Poundation Symposium 121, John Wiley Sons, Inc., New York, 1986, pp. 40—58. 

In addition, the linear, biogenic polyamines, spermidine and spermine, originally isolated from human sperm19), have been long known. Their structures are shown below. 

Catecholamines are biogenic amines with a catechol (o-dihydroxy-benzol) structure. They are synthesized in nerve endings from tyrosine and include dopamine, noradrenaline (norepinephrine) and adrenaline (epinephrine). 

Reuptake transporters are structures within the cell membranes of the presynaptic nerve terminal that serve to transport biogenic amines released from vesicles back into the nerve cell. These structures are targets for antidepressants, which block the transporter, thus increasing the bioavailability of neurotransmitters at postsynaptic receptors. 

Much of the geographic variability in sedimentary ( Paxs/ °Thxs) observed in modern sediments may be explained by variability in the composition of biogenic particles arising from variability in the structure of the planktonic ecosystem. This can be inferred from the composition-dependence of F(Th/Pa) (Fig. 8), and is shown explicitly by the relationship between sediment trap ( Paxs/ °Thxs) and the opal/calcite ratio of the trapped particles (Fig. 9). Sediment trap ( Paxs/ °Thxs) also exhibits a positive relationship with the mass flux of particles, but the correlation is poorer than that with particle composition (Fig. 9). Indeed, the relationship between particulate ( Paxs/ °Thxs)... 

Biogenic fossils Can some of the structures seen in meteorites, especially ALH84001, be attributed to astrobiology on other planets and what is the size of a cell ... 

Histamine is a mediator of several physiological and pathological processes within and outside the nervous system 249 The chemical structure of histamine has similarities to the structure of other biogenic amines, but important differences also exist 250... 

The chemical structure of histamine has similarities to the structures of other biogenic amines, but important differences also exist. Chemically, histamine is 2-(4-imidazolyl)ethylamine (Fig. 14-1). The ethylamine backbone is a common feature of many of the amine transmitters (e.g. dopamine, norepinephrine and serotonin). However, the imidazole nucleus, absent from other known transmitters, endows histamine with several distinct chemical properties. Among these is prototypic tautomerism, a property that permits it to exist in two different chemical forms (Fig. 14-1). The tautomeric properties of histamine are thought to be critical in the... 

Rudnick, G. (1997) Mechanisms of biogenic amine neurotransporters, in Neurotransmitter Transporters Structure, Function, and Regulation 1st ed. (Reith, M. E. A., ed.), Humana Press, Totowa, NJ, pp. 73-100. 

The biogenic amines are the preferred substrates of MAO. The enzyme comes in two flavors, MAO-A and MAO-B, both of which, like FMO, rely on the redox properties of FAD for their oxidative machinery. The two isoforms share a sequence homology of approximately 70% (81) and are found in the outer mitochondrial membrane, but they differ in substrate selectivity and tissue distribution. In mammalian tissues MAO-A is located primarily in the placenta, gut, and liver, while MAO-B is predominant in the brain, liver, and platelets. MAO-A is selective for serotonin and norepinephrine and is selectively inhibited by the mechanism-based inhibitor clorgyline (82). MAO-B is selective for /1-phcncthylaminc and tryptamine, and it is selectively inhibited by the mechanism-based inhibitors, deprenyl and pargyline (82) (Fig. 4.32). Recently, both MAO-A (83) and MAO-B (84) were structurally characterized by x-ray crystallography. 

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