An SPS-RS Technique for the Fabrication of SrMoO4 Powellite Mineral-like Ceramics for 90Sr Immobilization.

This paper reports a method for the fabrication of mineral-like SrMoO4 ceramics with a powellite structure, which is promising for the immobilization of the high-energy 90Sr radioisotope. The reported method is based on the solid-phase "in situ" interaction between SrO and MoO3 oxides initiated under spark plasma sintering (SPS) conditions. Dilatometry, XRD, SEM, and EDX methods were used to investigate the consolidation dynamics, phase formation, and structural changes in the reactive powder blend and sintered ceramics. The temperature conditions for SrMoO4 formation under SPS were determined, yielding ceramics with a relative density of 84.0-96.3%, Vickers microhardness of 157-295 HV, and compressive strength of 54-331 MPa. Ceramic samples demonstrate a low Sr leaching rate of 10-6 g/cm2·day, indicating a rather high hydrolytic stability and meeting the requirements of GOST R 50926-96 imposed on solid radioactive wastes. The results presented here show a wide range of prospects for the application of ceramic matrixes with the mineral-like composition studied here to radioactive waste processing and radioisotope manufacturing.

Azide derivatives of soybean oil and fatty esters.

An environmentally friendly water-based pathway to form the azide derivatives of soybean oil and fatty esters is reported. This entails first the formation of epoxides and then the azidization of the epoxides. The azidization reaction is carried out at high yields in water with only a small amount of an ionic liquid as a catalyst. The distribution of azide and alcohol functionalities on the fatty acid moiety is approximately random. This reaction has been applied to methyl oleate, methyl linoleate, soybean oil, and methyl soyate. The resulting structures have been studied by NMR.

Synthesis of hydroxy thio-ether derivatives of vegetable oil.

Bio-based additives are desirable commodities due to their eco-friendly nature. These additives can demonstrate physical and chemical properties comparable to those of conventional mineral oil-based products. Sulfur incorporated triacylglycerol can function as an antiwear/antifriction additive for lubricants. The synthesis of four useful hydroxy thio-ether derivatives of vegetable oils, from commercially available epoxidized soybean oil and common organic thiols, is reported in this paper. The common thiols used herein were 1-butanethiol, 1-decanethiol, 1-octadecanethiol, and cyclohexyl mercaptan. Currently, there is no reported literature describing the synthesis of hydroxy thio-ether derivatives of vegetable oil. The reaction was monitored, and products were confirmed by NMR and FTIR spectroscopies. Experimental conditions involving various thiols, solvent, catalyst amount, time, and temperature were optimized for research quantity and laboratory scale-up. The synthetic process retains the vegetable oil structure, eliminates polyunsaturation in the molecule, and adds polar functional groups on triacylglycerol. These products can be used as agriculturally-based antiwear additives for lubricant applications.

Flexibilized gelatin film-based artificial skin model: I. Preparation and properties of the films.

A method was developed to prepare a simple, flexibilized gelatin film-based artificial skin model. The films are tough, adhere to open wounds spontaneously, are permeable to body fluids, and can release incorporated bioactive compounds over 4-5 days.

Flexibilized gelatin film-based artificial skin model: II. Release kinetics of incorporated bioactive molecules.

Any delivery system for bioactive molecules should have the ability to release the compound in question in a reproducible and predictable way over a certain period. For artificial skin models that are designed to enhance healing by the use of growth factors, this requirement poses another problem: the design of a delivery method that can provide a realistic assessment of the release kinetics. This means that the design should "mimic" conditions encountered in an open wound, i.e., only a certain part of the film can face the wound, from which it can absorb wound fluid that will dissolve the incorporated bioactive molecule and bring it to the open wound. Such a system has been developed and the release of 125I-labelled insulin, incorporated into flexibilized gelatin films, has been determined. The details of this study follow.

Protein-polymer grafts, IV. A. Modification of amino acids: IIai. Modification of free lysine with reductive arylation.

Inability to increase the yield of reaction between 2,4 dihydroxybenzaldehyde and gelatin beyond 55 and 60% has led to an extensive investigation of reductive alkylation with free lysine. Even with free lysine, the extent of reaction was about 60%. Since this could be attributed to the electron donation by the phenolic hydroxyls, reductive alkylation was performed between o-, m-, and p-nitrobenzaldehydes and free lysine; o- and m-nitrobenzaldehyde were ineffective in increasing the yield while with p-nitrobenzaldehyde a yield of 72% was achieved. The unreacted 28% of the lysines are susceptible to epichlorohydrin. These results suggest that the slow, reversible first step in reductive alkylation, the formation of the Schiff's base, is responsible for the low yield.

Novel materials from protein-polymer grafts.

Proteins are the most underrated and under-used polymers: their impressive properties include infusibility, great mechanical strength and inherent adhesive capability due to a highly flexible backbone and many functional side chains. The notion of moisture sensitivity of proteins is not universally true. Barnacle cement (which can adhere to Teflon) and mussel and clam byssus, all of which are 99% protein, set in the presence of water and resist enzymatic as well as chemical degradation at ambient temperature. This observation suggests that proteins that are capable of tight three-dimensional cross-linking can overcome sensitivity to moisture and enzymatic attack. It should then be possible to achieve similar resistance by appropriate chemical manipulation of proteins, leading to cross-linking. We have achieved such a result with an ordinary protein, commercially available gelatin, which was chemically modified and then epoxidized. When cured such a material binds to metals and plastics. Any protein that has modifiable amino acids can be used for this purpose.

Protein signatures--a novel way to classify proteins.

A method is developed to classify proteins by establishing their familial identity based on the presence and the absence of characteristic signature dipeptides. It is hoped that this method will lead to the establishment of a theoretical basis for the determination of interrelationships among proteins.

Amino-acid neighborhood relationships in proteins. Breakdown of amino-acid sequences into overlapping doublets, triplets and quadruplets.

A method has been developed which allows the breakdown of an amino-acid sequence of proteins into overlapping di-, tripeptides, etc. The frequency of their distribution provides very convincing evidence that these sequences are non-random. These peptides have been demonstrated to be capable of being used as an objective key for the classification of organisms, and of proteins. It is also believed that they can be useful in increasing the accuracy of the prediction of protein folding.

A unique method to represent proteins.

A new method, based on the frequency distribution of amino-acid pairs, is developed to represent proteins. The method can accommodate and convey all of the chemical and many of the physical properties of proteins. It also lends itself to classification of organisms from which a protein is obtained (Erhan, 1978) and also to classification of protein families (Erhan, in preparation).

Probable mechanism of enzyme evolution: how did EBG of E. coli originate?

A mechanism is proposed for the formation of Ebg-evolved beta galactosidase-of E. coli based on the following assumptions: 1. In the presence of lactose, certain proteins being translated bind to their m-RNA-ribosome complexes; 2. This binding interferes with the release of m-RNA from the bacterial chromosome, marking the gene; 3. Thereupon a cytosine specific methylase and methyl cytosine deaminase pair, modify - mutate - the marked gene; 4. The result, after five or so mutations, is a new gene capable of coding for a different protein which can split lactose; 5. I propose that this enzyme pair has evolved to produce mutations internally, when need arises, as is the case here; 6. This may be a general mechanism through which drug resistance and detoxification of a novel chemical, could be achieved in bacteria; 7. All of these ideas are experimentally testable.

Attempts at simulating evolution by a computer: I. evolution of proteins under prebiotic conditions.

The effect of random mutations of five identical pentapeptides that have been inserted arbitrarily along a 100 amino acid-long protein chain has been studied by computer simulation. The method used was the application of mutation probability matrix for 2 PAMs of Dayhoff (1972) repeatedly to obtain the desired length of time. The results indicated that, given sufficient length of time, even the identical peptides could become drastically altered and in order to recognise them as stemming from the same origin one has to use reasonable statistical significance thresholds.

Systematics: use of protein nearest neighbour frequency distribution as an objective key.

Although it is one of the oldest of modern disciplines, systematics has always been a science practised in a highly personalised and subjective way because of the need to rely on morphological characteristics of the living organisms, as well as the fossil remains, for their classification. Recent studies on the amino acid nearest neighbours, however, enable one to have an objective key for classifying organisms as well as their relationships.

Origins of the first cell. A new model for the spontaneous formation of the first living cell based on a novel approach.

Whether proteins or nucleic acids were responsible for the emergence of life has been debated for a long time. Taking the observation that families of proteins display a remarkable invariance of their amino acid sequence around critical regions, such as active/binding sites, even though these proteins may represent considerable evolutionary diversity, as the naturally provided evidence of evoluntionary selection of working system, the idea is developed that: 1. Proteins had to have been first informational macromolecules that were necessary and sufficient to lead to the emergence of life; 2. it is impossible for a nucleic acid molecules to have formed, by chance, whose base sequence could yield a biologically active protein. A model is proposed to account for the emergence of the first successful cell according to this approach.

Potential of the amino acid homology studies: homologies found between beta-galactosidase and lac repressor of E. coli.

Significant amino acid homologies were found between beta-galactosidase fragments and lac repressor of E. coli using a sliding match according to Greller and Erhan (1974). Since both of these proteins can recognise and bind galactose moiety, we propose that the homologous regions represetn galactose binding site(s) on both proteins. Possible application of homology studies to problems of protein and nucleic acid chemistry is also discussed.

Evolution of the transfer RNA molecule.

Base sequences of many transfer RNA (tRNA) species obtained from different sources contain homologous regions. These homologies, which are 6 to 20 nucleotides long, occur both within the same tRNA molecule and between many different tRNA molecules repeatedly. Since it is very unlikely an 80 or so nucleotide long tRNA molecule could have been formed at once, under primordial conditions, we propose that the homologous oligonucleotides found within the tRNA molecules to-day represent the earliest adapter from which tRNA molecules have evolved.

Symmetry patterns in trypsinogen.

When the primary structure of bovine trypsinogen is searched for the existence of regularities, according to Greller & Erhan (1974), one finds eight pairs of peptides, arranged in a symmetrical pattern along the molecule. These peptides cover 49% of the length of the molecule-112 of the 227 amino acids-and each pair folds in a similar way. This observation is in agreement with the observation that "Trypsin folds into two halves, each of which contains a pseudo-cylindrical arrangement of hydrogen bonds...", Stroud et al. (1971). Thus the above mentioned method is capable not only of detecting regulatities along the primary structure but also of predicting the folding of a protein.

Is there a protein ligase?

Results obtained from experiments dealing with mammalian, bacterial, phage and mitochondrial protein biosynthesis as well as certain enzymatically performed amino acid replacement studies on Kunitz trypsin inhibitor strongly suggest that protein ligation may be occuring in vivo. Amino acid substitution experiments prove the reversibility of endopeptidase reactions, and protein ligation is the reverse of endopeptidase reaction. These experiments are discussed in detail and the suggestion is made that ligation may also be useful in the repair of certain essential proteins which may become damaged.