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By a radiometric method using C14 labelled amino acid mixture it was established that the Streptococcus pyogenes A49 L-forms cells invade tissue cultures MK and F in a similar degree as parent bacterium cells. The L-form cells are not able to enter the HeLa and Pulmo tissue culture cells but the parent bacterium cells produce well expressed peak of isotope take-up at the 8th hour of the observation.

Chymosin molecules in the crystal lattice have Tyr77 occluding the S1 S3 substrate binding pockets suggesting that the enzyme is self-inhibited. An analysis of this structure in conjunction with its comparison with pepsin has shown that this is most probably an intrinsic property of the enzyme. It also indicates that chymosin's substrate specificity may be dependent upon the ability of the substrate to displace the tyrosine ring from the binding pockets. This analysis also implies that active and self-inhibited forms of other aspartic proteinases can exist in solution helping to explain the results of kinetic studies of these enzymes.

Bme 361 I, a new site-specific type II deoxyribonuclease, was purified from Bacillus megaterium 361 by chromatography on phosphocellulose P 11 and hydroxylapatite. The enzyme recognizes and cleaves the nucleotide sequence 5'-GG decreases CC-3' in double-strand DNA. Thus it is a true isoschizomer of deoxyribonucleases Hae III and BspR I.

The method for analysis of microorganisms for the presence of the modification-restriction systems has been developed. The method has permitted to detect more than 10 new producing strains of restrictases including microorganisms of Rhizobium genus. Some of them are promising for practical use. It has been shown that using selection of clones the strain productivity can be increased. The purification process for the majority of restrictases has been proposed. Some physical and catalytic properties of new enzymes have been studied.

A new site-specific restriction endonuclease Rme211 from Rhizobium meliloti has been shown to recognize the following nucleotide sequence 5'-ATCGAT-3' in the double-stranded DNA. Thus, the enzyme is a true isoschizomer for restriction endonucleases Bsu151 and ClaI.

Pepsin has several properties which are markedly different from those common for other proteins. It has a very low pH optimum for the hydrolysis of different substrates and a high activity at pH 2. This implies a very stable tertiary structure under conditions in which many proteins are fully denatured. These properties of pepsin are critical for its physiological function which takes place in the extreme acid conditions of the gastric lumen. There the unfolded hydrophobic cores of the proteins to be cleaved are exposed to the first hydrolytic attack by pepsin. Another very specific property of pepsin is its extremely low isoelectric point. It has a net negative charge in the range of low pH values including the pH optimum for catalytic activity. The proteins to be cleaved have a net positive charge in this range of pH. These molecular features of pepsin are closely interdependent as all of them are the consequence of the specific arrangements and interaction of the charged groups in the three-dimensional fold of the enzyme. Data on the refined porcine pepsin A structure at 1.8 A resolution (Sielecki et al., 1990) have pointed towards their explanation. Porcine pepsin has also been refined at 2.3 A resolution in the monoclinic crystal form by Abad-Zapatero et al. (1990) and in the hexagonal crystal form by Cooper et al. (1990).

Domains of aspartic proteinase molecules have the same fold (Tang et al., 1978) while their primary structures show no homology except small segments of a few amino acid residues located in the region of the active site in the three-dimensional structure. One may ask: is it possible to detect a common specific property of amino acid sequences of both domains which can explain the tendency of their chains to fold by the same manner? In other words does a consensus template for the specific aspartic proteinase fold exist? Interactions between different segments of a polypeptide chain providing formation of a central hydrophobic core of a protein molecule determine mainly the geometrical type of protein folding. If a consensus template for the specific aspartic proteinase fold really exists it must concern the formation of central hydrophobic cores in domains.

The molecular structure of the archetypal aspartic proteinase, porcine pepsin (EC 3.4.23.1), has been refined using data collected from a single monoclinic crystal on a twin multiwire detector system to 1.8 A resolution. The current crystallographic R-factor (= sigma parallel to Fo/-/Fc parallel to/sigma/Fo/) is 0.174 for the 20,519 reflections with /Fo/ greater than or equal to 3 sigma (Fo) in the range 8.0 to 1.8 A (/Fo/ and /Fc/ are the observed and calculated structure factor amplitudes respectively). The refinement has shown conclusively that there are only 326 amino acid residues in porcine pepsin. Ile230 is not present in the molecule. The two catalytic residues Asp32 and Asp215 have dispositions in porcine pepsin very similar to the dispositions of the equivalent residues in the other aspartic proteinases of known structure. A bound solvent molecule is associated with both carboxyl groups at the active site. No bound ethanol molecule could be identified conclusively in the structure. The average thermal motion parameter of the residues that comprise the C-terminal domain of pepsin is approximately twice that of the residues in the N-terminal domain. Comparisons of the tertiary structure of pepsin with porcine pepsinogen, penicillopepsin, rhizopus pepsin and endothia pepsin reveal that the N-terminal domains are topographically more similar than the conformationally flexible C-terminal domains. The conformational differences may be modeled as rigid-body movements of "reduced" C-terminal domains (residues 193 to 212 and 223 to 298 in pepsin numbering). A similar movement of the C-terminal domain of endothia pepsin has been observed upon inhibitor binding. A phosphoryl group covalently attached to Ser68 O gamma has been identified in the electron density map of porcine pepsin. The low pKa1 value for this group, coupled with unusual microenvironments for several of the aspartyl carboxylate groups, ensures a net negative charge on porcine pepsin in a strongly acid medium. Thus, there is a structural explanation for the very early observations of "anodic migration" of porcine pepsin at pH 1. In the crystals, the molecules are packed tightly into a monoclinic unit cell. There are 190 direct contacts (less than or equal to 4.0 A) between a central pepsin molecule and the five unique symmetry-related molecules surrounding it in the crystalline lattice. The tight packing in this cell makes pepsin's active site and binding cleft relatively inaccessible to substrate analogs or inhibitors.

Chymosin is distinguished by a high level of milk-clotting activity which is the consequence of the specific cleavage of the Phe(105)-Met(106) bond of kappa-casein. Based on modelling considerations it was proposed that milk-clotting activity of chymosin is associated with electrostatic interactions of a charged segment His-Pro-His-Pro-His (98-102) of casein and the outer loop of the enzyme containing Glu-244,Asp-246 and Asp-248.

Comparative analyses have been carried out on the dynamics of invasion of cell cultures from epithelioid (MK and HE-p-2) and fibroblast (mice fibroblasts) types with strain Escherichia coli 0 18 isolated and characterized earlier, as well as on the invasion of the viscera of inbred mice (BDF1) after subcutaneous (foot pad lesion test) and intravenous inoculation with the same strain. It was established that the realization of the invasion potential of E. coli 018 depends on the cell culture used: cell cultures of epithelioid type are much more sensitive. The development of the infectious process and the changes in the number of bacteria in the viscera of the inoculated mice for both ways of introduction of the agent were of the same type. The infectious process after subcutaneous inoculation was accompanied with serious orchitis and progressive inflammatory necrotic changes in the inoculated paws leading to demarcation of the whole limb.

Using the most effective rapid method for the detection of restriction endonucleases (ENases) in microorganisms, 32 thermophilic producers have been isolated. All strains belong to the genus Bacillus. Thermostable isoschizomers of ENases, such as AvaI, BbvI, BbvII, BelI, BsasI, BsiYI, BsrI, BstEII, BstNI, Cfr101, ClaI, FspI, HaeIII, HpaII, Ksp632I and SfeI, were isolated.

An account of x-ray crystallographic studies of monoclinic porcine pepsin crystals is presented. The chain fold specific for aspartyl proteases is described in detail. As the results of 2-A refinement have shown, the actual structure is that of ethanol-inhibited pepsin. The structure, although close to those of fungal aspartyl proteases, has some specific features: one of them is an insertion near the S'1 site which restricts the position of dipeptide substrates and makes their productive binding more probable than in the fungal enzymes. 3-A resolution data on the binding of the dipeptide phenylalanyl-diiodotyrosine methyl ester are discussed.

1. Under the action of sodium methoxide in methanol 2,3-epoxypinane forms trans-2(10)-pinen-3-ol (mixture ofl- and dl-forms) and 3-pinanone (mixture of d- and dl-forms). 2. Under the conditions of the reaction of 2,3-epoxypinane with methanol 3-pinanone may be formed in two ways: 1) mainly directly by the isomerization of the epoxide into the ketone, and 2) by the isomerization of the primary reaction product 2(10)-pinen-3-ol under the action of the base.

1. The primary oxidation of terpinolene at the semicyclic double bond was confirmed, and it was shown that the dioxide has a trans-structure. 2. Terpinolene monoxide exists in solution in the form of a mixture of two half-chair forms; for the dioxide the boat conformation is stable.

1) The main part (61.5–73.4%) of the total amount of aromatic compounds which are present in catalytic gas oils are polycyclic compounds. 2) The polycyclic aromatic compounds consist of both pure aromatic and of hydroaromatic hydrocarbons; no more than one naphthene ring being present in a molecule of the latter hydrocarbons. The number of caron atoms in the side chains is 1.3–2.4. 3) In comparison with phenol, furfurole has a higher selectivity with respect to the polycyclic aromatic compounds. 4) The dissolving capacity of the phenol is somewhat higher for phenol than for furfurole. 5) The temperature range for this extraction of catalytic cracking gas oil by furfurole is 1.5 times greater than for phenol. 6) The optimum furfurole flow rate for the extraction of catalytic cracking gas oil is 100% by volume based on the raw material.

1. In a study of the selective extraction of heavy gas oils produced by catalytic cracking of vacuum distillates from different crude sources, it was shown that raw material with a C. I. above 120, for the production of special carbon blacks, can be obtained by using zeolitic catalyst in the cat cracker, with a subsequent extraction operation on the heavy catalytic gas oil distilling above 350‡C. 2. In order to obtain raw material with sulfur content below 1.8% for the production of highly structurized, very fine carbon blacks, and high-sulfur feedstock used in catalytic cracking must first be hydrotreated; alternatively, the cat cracker may be operated on feedstock cut from low-sulfur crudes. In either case, the heavy catalytic gas oil is extracted to obtain the desired raw material for carbon black production.

A study was made of the isomerization of 2,3-epoxypinane and 3,4-epoxycarane by means of lithium diethylamide. 2,3-Epoxypinane is isomerized into trans-2(10)-pinen-3-ol, whereas 3,4-epoxycarane forms a mixture of alcohols: 3(10)-caren-4-ol, p-mentha-1,5-dien-8-ol, and m-mentha-4,6-dien-2-ol.

Analysis is made of the system of parallel chain molecules which has a long-range order in the arrangement of the structural units along the chains, and a short-range order in the packing of molecules. A solution has been obtained of the problem of scattering x-rays on such a system. Analysis of the correspodence between theoretical results and the results for certain fibrous proteins and polymers has been made. This analysis shows that in some parts of these substances there are regions where the parallel chains are arranged without any correlation to the packing of the units of neighboring chains.

1. In Cr−Ni martensitic steels with 11% Cr and 9% Ni the α→γ transformation at heating rates below 50 deg/sec is accompanied by redistribution of chromium and nickel between the α and γ phases. 2. The austenite formed in the partial α→γ transformation contains more chromium, nickel, and probably more molybdenum than the α phase. 3. The enrichment of austenite in chromium, nickel, and other elements in the process of the α→γ transformation in steels of the Kh11N9 type is evidently one reason for the stabilization of austenite during tempering of these steels at α→γ transformation temperatures.

1. We synthesized terpinolene monoxide (4,8-epoxy-p-menthene-1) and dioxide for the first time and confirmed their structure from their NMR and IR spectra. 2. The isomerization of 4,8-epoxy-p-menthene-1 under the influence of zinc bromide was studied. Two isomeric ketones with the composition C10H16O were isolated in individual form; analysis of their PMR spectra provided a basis for assigning them a seven-member ring structure.

1. A feasibility study has been carried out for the utilization, in carbon black production, of the heavy tars obtained in existing USSR ethylene units operating on naphtha, gaseous hydrocarbons, or mixed feedstocks. 2. The heavy-tar yield amounts to 3 to 5% of pyrolysis feedstock weight. 3. In the majority of cases, the heavy tar now being produced will satisfy the requirements imposed on the quality of prospective raw materials for carbon black production.

1. Glycyl-L-proline, L-prolylglycine, benzyloxycarbonyl-L-proline, and glycyl-L-proline anhydride were synthesized and were obtained in the form of monocrystals. 2. The first stage of the x-ray structure analysis of the synthesized compounds was carried out.

1. The gas oil cuts obtained by cat cracking vacuum distillates from most domestic [USSR] crudes can be used as starting material in the production of carbon black, with use of the extraction method. 2. The total content of bi- and polycyclic naphthenes and aromatics in the cat cracker feed can be used to determine the approximate yields of the gas oil cuts. 3. If the hydrocarbon composition is known for the cat cracked gas oil (270–420°C or 195–420°C), the curve given in Fig. 3 can be used to determine the yield of extract, i.e., the yield of carbon-black feedstock. 4. This investigation was performed with amorphous aluminosilicate catalysts, but the conclusions may be extended to zeolitic catalysts as well. The only factor that should be kept in mind is that the conversion of hydrocarbons (primarily paraffinic) is higher on zeolitic catalysts, so that the cat cracked gas oil cuts will be more highly aromatic but the yields of gas oil will be lower. However, the extract yield, calculated on gas oil, will be higher.

The hydrolysis of chloroacetophos in water includes the parallel cleavage of acetic acid, hydrochloric acid and methanol. The ratio of the products, formed in the parallel steps, was determined, and we also determined the total rate constant for the hydrolysis of chloroacetophos.

1. It has been shown that the 250–420°C fraction from the thermal cracking of semitar can be used in the production of carbon black stock by selective extraction. 2. Furfural is the most suitable extraction solvent. 3. It is recommended that the thermal-cracking residue should be used fully or partially in the production of carbon black stock.

1. It has been shown, that, in principle, high-quality starting material for carbon black manufacture can be produced from an appropriate mixture of heavy and polymeric gasoils produced in various types of catalytic cracking units, and from the residue left after distillation of the 270°C fraction from the appropriate mixture of light and heavy gasoils produced in units with a fluid catalyst bed. 2. Extracts from the starting materials mentioned meet all requirements imposed on a starting material for the production of active carbon blacks.

The pathogenetic community of various viral neuroinfections different in their form and course points out that the use of means targeted at correction of the immune system functions is desirable. As a result of using combined immunotherapy methods the authors have obtained positive results in treating 38 patients suffering from some acute and chronic neuroinfections (grave local forms of acute tick-borne encephalitis, progredient forms of the same encephalitis, disseminated sclerosis, disseminated encephalomyelitis). Interrelations between the immunity factors are studied, and their role in the therapeutic effect obtained is discussed. The scheme and the result of the treatment, as well as general principles of dynamic observation and treatment of those patients are presented.

The effect of some adenyl precursors of DNA synthesis on the mutagenic activity of hydroxylamine (HA) is studied. It is shown that the addition of adenine to a suspension of Escherichia coli B cells increases the yield of mutants by more than two times as compared with HA alone. The effects of adenosine, AMP and dAMP are somewhat different. It is suggested that the increase of the HA mutagenic effect produced by the addition of adenine may be due to: 1) the excess of the amount of adenylic precursors of DNA synthesis over guanilic ones, which promotes the erroneous base-pairing during the replication of the HA modified template; 2) the modification of adenylic precursors by HA into N6-oxy-dATP, and their incorporation into DNA. The mutagenic effect of N6-hydroxyadenosine, the product of the adenine modification by HA, in E. coli B pur- was studied. The experiments showed that N6-hydroxyadenosine induced about 1% of mutations, a relatively low lethal effect (the cell survival was 80%), and provided a high mutagenic action of this compound.

The universal phenomenon of virus persistence is considered to be a regular phenomenon primarily meeting the interests of the host. Examinations of 1112 patients with various diseases of the nervous system revealed a certain dependence of macroglobulin measles antibody upon the character of the disease and the intensity of demyelinization process. These data do not suggest the etiological role of the persisting measles virus in the genesis of multiple sclerosis and a large group of other nervous system diseases (SSPE). Similar results were obtained in analogous examinations of patients for macroglobulin mumps antibody. The results indicate the role of persisting viruses in the formation of solid specific immunity as well as their importance for nonspecific protection against other immunologically similar diseases. Virus persistence is considered to be a certain antiviral strategy of the body based on accumulation in the life course of a considerable number of persisting viruses on which both specific and nonspecific antiviral protection is founded. Congenital or acquired defects of immunity cause the development of the persisting infection and appearance of some chronic diseases of the nervous system.

The results of complex examination of 489 patients suffering from chronic neuroinfections (progressing forms of tick-borne encephalitis, disseminated sclerosis, disseminated encephalomyelitis, subacute sclerosing panencephalitis, etc.) are presented. An analysis of the results of virological, immunological, genetic and electrophysiological examinations, as well as the results of kinesotherapy has demonstrated a definite role of hereditary peculiarities of the immune mechanisms and the nervous system in the genesis of those diseases, as well as certain common features of the pathogenetic mechanisms. This enables one to outline some general principles of the therapy of those diseases.

This is the first paper in the series of publications on the detailed description of different aspects of pepsin structure. It concerns the domain structure of the enzyme and the topology of the arrangement of beta-strands in pepsin and related aspartic proteases, this topology being quite different from that of all other beta-proteins. The topology, molecular symmetry and the close proximity of the N- and C-termini of domains suggest that at the first stages of evolution polypeptide chains of some preproteins could be closed in rings, which become open at the subsequent stages. Their genes duplicated twice, and the fusion process resulted in a gene consisting of similar parts.