In the recent decades, antibacterial peptides have occupied a strategic position for pharmaceutical drug applications and became subject of intense research activities since they are used to strengthen the immune system of all living organisms by protecting them from pathogenic bacteria. This work proposes a simple and easy statistical/computational method through a peptide polarity index measure by which an antibacterial peptide subgroup can be efficiently identified, that is, characterized by a high toxicity to bacterial membranes but presents a low toxicity to mammal cells. These peptides also have the feature not to adopt to an alpha-helicoidal structure in aqueous solution. The double-blind test carried out to the whole Antimicrobial Peptide Database (November 2011) showed an accuracy of 90% applying the polarity index method for the identification of such antibacterial peptide groups.

Clay minerals are considered important to chemical evolution processes due to their properties, ancient origin, and wide distribution. To extend the knowledge of their role in the prebiotic epoch, the adsorption sites of adenine, adenosine, AMP, ADP, ATP, Poly A, uracil, uridine, UMP, UDP, UTP and Poly U on sodium montmorillonite are investigated. X-ray diffraction, ultraviolet and infrared spectroscopy studies indicate that these molecules distribute into the interlamellar channel and the edge of the clay crystals. Monomers are adsorbed predominantly in the interlamellar channel, whereas polymers adsorb along the crystal edges. Such behavior is discussed mainly in terms of bulk pH, pK(a) of the adsorbate, and Van der Waals interactions.

SummaryThe viscosity, density, and sedimentation characteristics of suspensions of whole and mechanically disrupted yeast cells were measured. Mechanical disruption increases the suspension viscosity and its nowNewtonian behavior. Experiments showed a good correlation between laboratory-and industrial-scale centrifugation results. IN T R 0 DUCT I 0 NMethods are now available for the industrial-scale mechanical disruption of microbial cells'*2 to isolate intracellular products. Following cell disruption it is normally necessary to remove the cell debris for product recovery.We have previously examined the clarification of mechanically disrupted yeast suspensions by rotary vacuum precoat filtrati~n.~ Centrifugation is the currently used alternative to filtration and this study is directed toward a better understanding of the use of this method.Performance predictions of solid-liquid separation by these methods depend on a knowledge of certain physical characteristics of the solids and the liquids in which they are suspended. A little information exists for whole cell suspension^.^.^ We have measured several properties using simple and readily available techniques that, although they do not justify a sophisticated analysis,6 do provide some useful information. This paper first describes laboratory studies on the viscosity, density, and sedimentation characteristics of disrupted bakers' yeast suspensions

This paper describes the possible effects of ionizing radiation arising from long-lived soluble radionuclides within clays, in particular 40K, at the epoch of the emergence of life on Earth. The free dispersion of soluble radionuclides constitutes an effective in situ irradiation mechanism that might have acted upon adsorbed nucleic bases and their derivatives on clays, inducing chemical changes on these organic molecules. Several types of well documented reactions for radiolysis of nucleic acid bases and their derivatives are known, even at low doses (i.e., 0.1 Gy). For example, estimates with a dose rate calculated from 40K from deep sea clays at 3.8 Ga ago, indicates that over a period of 1000 years the amount of organic material transformated is 1.8 X 10(-7) moles/kg-clay. Although ionizing radiation may also induce synthetic reactions with prebiological interest, all in all these considerations indicate that nucleic acid bases and their derivatives adsorbed on clays were exposed for long periods to degradation conditions. Such situation promotes decomposition of organic molecules rather than protection of them and enhancement of farther polymerization, as it has been usually taken for granted.

SummaryA lo00 liter fermentor has been used to produce a continuous feed of Escherichia coli containing a high level of p-galactosidase. We have investigated the individual unit operations for the isolation of the enzyme :cell disruption, nucleic acid removal, protein precipitation, and solid-liquid separation after each stage. Using the information obtained we have been able to operate a semicontinuous process which when fully continuous would yield 100 g proteidhr, comprising 23% p-galactosidase.