Effects of winter flooding on phosphorus dynamics in rice fields

Limnology - Controlling phosphorous (P) loads from rice fields is important for the conservation of aquatic ecosystems, in part because P is relatively concentrated at its sources. Recently, winter...     

Studies on peptides CLVIII. Model experiments for the synthesis of open-chain unsymmetrical cystine-peptides

Treatment of a mixture of Cys(R)(O) and Cys(R) with an acid was found to generate cystine in fairly good yields, when suitable R, R, and an acid were selected. An unsymmetrical cystine peptide was prepared by treatment of a mixture of Z(OMe)-Cys(R) (0)-Ala-NH₂ (R=Acm or MBzl) and Z(OMe)-Cys(MBzl)-Gly-OBzl with TFA or 1 M TFMSA/TFA.³ Oxytocin was obtained in an excellent yield by TFA treatment of the protected peptide containing Cys(Acm)(0) and Cys(MBzl). Thus, formation of the disulfide bond was found feasible at the position of Cys(R) (0).The following abbreviations are used Boc t-butyloxycarbonyl - Z(OMe) p-methoxybenzyloxycarbonyl - MBzl p-methoxybenzyl - Acm acetamidomethyl - Bzl benzyl - Ad l-adamantyl - tBu t-butyl - TFA trifluoroacetic acid - TFMSA trifluoromethanesulfonic acid - TMSOTf trimethylsilyl trifluoromethane sulfonate     

Examination of protein sequence homologies: III. Ribosomal protein YS25 fromSaccharomyces cerevisiae and its counterparts fromSchizosaccharomyces pombe,rat liver,andEscherichia coli

Summary The sequences of the ribosomal proteins YS25, SP-S28, RL-S21, and Ec-S6, fromSaccharomyces cerevisiae, Schizosaccharomyces pombe, rat liver, andEscherichia coli, respectively, have been examined using a computer program that searches for homologous tertiary structures. Matrices of comparisons among the eukaryotic sequences show that they match each other sequentially without any internal gaps. The average values of the correlation coefficients obtained from the comparison matrices are higher for the first halves of the sequences than for the latter halves. This result suggests that the first halves of the sequences may represent a more important domain than the latter halves. The comparison matrices between the eukaryotic and bacterial sequences of ribosomal proteins, however, do not show sequentially arranged homology, though there are six well-matching segments arranged in different orders in the two types of sequences. This implies that the eukaryotic sequences of the ribosomal protein were reconstituted by two internal transpositions and six deletions of 4–12 residues each from the ancestral sequence during the divergence between bacterial and eukaryotic genes. These findings may give insight into structural and quantitative studies of evolutionary divergence between eukaryotes and prokaryotes.     

Triterpenes from Periandra dulcis roots

Three oleanane triterpenes were isolated from the roots of Periandra dulcis,and identified as 3β-hydroxy-25-al-olean-18-en-30-oic acid (periandric acid I), 3β-hydroxy-25-al-olean-12-en-30-oic acid (periandric acid II) and 3-oxo-25-hydroxy-olean-12-en-30-oic acid. The former two compounds (periandric acids I and II) were identical with the aglycones obtained by hydrolysis of periandrin I and II, respectively and the latter one was a new triterpene.     

A novel anti-HIV synthetic peptide, T-22 ([Tyr5,12,Lys7]-polyphemusin II).

Tachyplesin and polyphemusin are antimicrobial peptides recently isolated from the hemocytes of horseshoe crabs (Tachypleus tridentatus and Limulus polyphemus). We synthesized them and their analogs and examined their antiviral activity against human immunodeficiency virus (HIV) type 1 in vitro. The infection of human T cells with the virus was markedly inhibited by some of them at low concentrations. In this structure-activity study, we found that [Tyr5,12, Lys7]-polyphemusin II, which was designated as T22, had extremely high anti-HIV activity. Its 50% inhibitory concentration (EC50) was 0.008 micrograms/ml, while its 50% cytotoxic concentration (CC50) was 54 micrograms/ml and these values were comparable to those of AZT. This result indicates that T22 would be a potential candidate for the therapy of HIV infection.     

The giant panda is closer to a bear,judged by α- and β-hemoglobin sequences

Summary Using - and -hemoglobin sequences, we made a maximum likelihood inference as to the phylogenetic relationship among carnivores, including the two pandas, giant and lesser. Molecular phylogenetic studies up to 1985 had consistently indicated that the giant panda is more closely related to the bear than to the lesser panda. In 1986, however, a contradictory tree was constructed, using hemoglobins and so on, in which the two pandas link together (Tagle et al. 1986). In contrast to that tree, our conclusion supports the close relationship between bear and giant panda. The surface impression of a close relationship between the two pandas drawn from pairwise amino acid differences is explained by a rapid rate of hemoglobin evolution in the bear compared to that in the two pandas.Offprint requests to: T. Hashimoto     

Inhibition of indoleamine 2,3-dioxygenase and tryptophan 2,3-dioxygenase by β-carboline and indole derivatives

β-Carboline derivatives inhibited both indoleamine 2,3-dioxygenase and tryptophan 2,3-dioxygenase activities from various sources. Among them, norharman is most potent for both enzymes from mammalian sources. Kinetic studies revealed that norharman is uncompetitive (K_i = 0.12 mm) with l-tryptophan for rabbit intestinal indoleamine 2,3-dioxygenase, and linearly competitive (K_i = 0.29 mm) with l-tryptophan for mouse liver tryptophan 2,3-dioxygenase. In addition, some β-carbolines selectively inhibited one enzyme or the other. Pseudomonad tryptophan 2,3-dioxygenase was inhibited by a different spectrum of β-carbolines. Such a selective inhibition by the structure of substrate analogs is more evident by the use of indole derivatives. Indole-3-acetamide, indole-3-acetonitrile and indole-3-acrylic acid exhibited a potent inhibition for mammalian tryptophan 2,3-dioxygenase, while they moderately inhibited the pseudomonad enzyme. However, they showed no inhibition for indoleamine 2,3-dioxygenase. These results suggest the difference of the structures of the active sites among these enzymes from various sources.     

Immunological evidence for structural homology between Drosophila melanogaster (S14), rabbit liver (S12), Saccharomyces cerevisiae (S25), Bacillus subtilis (S6), and Escherichia coli (S6) ribosomal proteins.

Specific antibodies directed against Drosophila melanogaster acidic ribosomal protein S14 were used in a comparative study of eucaryotic and procaryotic ribosomes by immunoblotting and enzyme-linked immunosorbent assays. Common antigenic determinants and, thus, structural homology were found between D. melanogaster, Saccharomyces cerevisiae (S25), rabbit liver (S12), Bacillus subtilis (S6), and Escherichia coli (S6) ribosomes.     

Hepatitis B virus envelope L protein particles. Synthesis and assembly in Saccharomyces cerevisiae, purification and characterization.

The hepatitis B virus envelope gene encodes three transmembrane proteins in frame; S, the product of S gene; M, the product of M (pre-S2 + S) gene; and L, the product of L (pre-S1 + pre-S2 + S) gene. Unlike the S and M proteins, attempts to efficiently synthesize L proteins and assemble them into L protein particles in various eukaryotic cells have been unsuccessful, probably because of the presence of the pre-S1 peptide with an unknown function which appears to be inhibitory to the host secretory apparatus. To investigate the role of the pre-S1 peptide, we constructed an L gene fused with a synthetic gene for chicken-lysozyme signal peptide (C-SIG) at the 5'-terminal and placed the resultant gene under the control of the yeast glyceraldehyde-3-phosphate dehydrogenase gene promoter. After the fused-C-SIG peptide was correctly processed by the yeast secretory apparatus, a yeast transformant synthesized a protein with a molecular mass of approximately 52 kDa at a level of 42% of the total soluble protein. Electron micrographic observation showed that the gene products assembled into 23-nm spherical and filamentous particles. The pre-S peptide of the gene product was deposited into the endoplasmic reticulum (ER) lumen and well-glycosylated. It seemed that the gene products were accumulated as particles in certain specific membrane structures of the yeast secretory apparatus. Moreover, both the amount of mRNAs specific for the L gene and the in vivo stability of the synthesized L proteins did not change significantly by the addition of the C-SIG gene. These findings indicated that, if the pre-S1 peptide penetrates the ER membrane efficiently, the L proteins can be synthesized cotranslationally, translocate across the ER membrane with its S region, and then assemble by themselves into the particle form. Therefore, the pre-S1 peptide may involve weak or reduced signal peptide activity for recognition by the secretory apparatus and/or for the transport of the pre-S peptide into the ER lumen.     

Dehydrodieugenol and its monomethyl ether from Virola carinata

The constituents of Virola carinata were established as dehydrodieugenol, its monomethyl ether and sitosterol.