亜鉛とヒスチジンならびにその関連化合物との錯体生成について

食品やその原料となる生物体には各種の金属元素とともに,多くの酸素－および窒素－配位子が含まれる。そこで金属元素の挙動を知るためには,これら金属－配位子の錯体形成に関する知識が必要となる。本報では,pHの異なる各種溶液中で生成するZn-HisおよびZn-含Hisジペプチド錯体について,電位差滴定曲線に基づいて考察した。考察の中心は,Zn錯体形成に関与する配位基と溶液のpHの関係であって,遊離Hisならびにペプチドの構成単位となったHis残基に分けて検討した。 まず,pH6以上の中性およびアルカリ性溶液中ではイミダゾール-NHとα-NH2が配位することを推測し,Fig.2の式IIIを示した。またHistaおよびHisMeと比較することによって,α-COOH基の影響もあり得ると考え,式VIIを示した。 次に,全く側鎖をもたないGlyとHisから成るジペプチドすなわちHisGlyおよびGlyHisを比較し,さらにGlyGlyと比べることによって,イミダゾール核がZn錯体を安定化させ,Zn(OH)2の沈澱形成をかなり抑制することについて考察を加えた。 この種の報文は少なく,とくにHisを含むペプチドとZnの錯体生成に関する報文は始めてのものである。Formations of Zn-histidine, -histamine, -histidine methylester, -histidylglycine, -glycylhistidine and -glycylglycine complexes in aqueous solution were examined by means of a potentiometric titration method. On the basis of the results obtained the possible chemical structures were given to the individual complexes. The main object of this investigation is to know what donor groups of histidine participate in the Zn-complex formation at a given pH value. In neutral and alkaline solutions above pH 6, the imidazole and the a-NH2 groups of histidine coordinate to the Zn ion and form the Zn-histidine (1:2) complex. In acidic solutions, the a-COOH group also coordinates and forms the Zn-histidine (1:1) complex together with the above two groups. The complexes formed by the participation of the imidazole group of histidine are considered to be more stable than the Zn-glycine or -glycylglycine complex by reason of the difficulty in the precipitation of Zn(OH)2 during the titrations. This was also the case for the Zn-histidine-containing dipeptide complexes

Carnosine content in skeletal muscle is dependent on vitamin B6 status in rats

Carnosine, a histidine-containing dipeptide, is well known to be associated with skeletal muscle performance. However, there is limited information on the effect of dietary micronutrients on muscle carnosine level. Pyridoxal 5'-phosphate (PLP), the active form of vitamin B6, is involved in amino acid metabolisms in the body as a cofactor. We hypothesized that enzymes involved in β-alanine biosynthesis, the rate-limiting precursor of carnosine, may also be PLP dependent. Thus, we examined the effects of dietary vitamin B6 on the muscle carnosine content of rats. Male and female rats were fed a diet containing 1, 7, or 35 mg pyridoxine (PN) HCl/kg for 6 weeks. Carnosine in skeletal muscles was quantified by ultra-performance liquid chromatography coupled with tandem mass spectrometry. In the gastrocnemius muscle of male rats, carnosine concentration was significantly higher in the 7 and 35 mg groups (+70 and +61%, respectively) than in the 1 mg PN HCl/kg group, whereas that in the soleus muscle of male rats was significantly higher only in the 7 mg group (+43%) than in the 1 mg PN HCl/kg group (P < 0.05). In both muscles of female rats, carnosine concentration was significantly higher in the 7 and 35 mg groups (+32 to +226%) than in the 1 mg PN HCl/kg group (P < 0.05). We also found that, compared to the 1 mg group, β-alanine concentrations in the 7 and 35 mg groups were markedly elevated in gastrocnemius muscles of male (+153 and +148%, respectively, P < 0.05) and female (+381 and +437%, respectively, P < 0.05) rats. Noteworthy, the concentrations of ornithine in the 7 and 35 mg groups were decreased in gastrocnemius muscles of male rats (-46 and -54%, respectively, P < 0.05), which strongly inversely correlated with β-alanine concentration (r = -0.84, P < 0.01). In humans, 19% lower muscle carnosine content was found in soleus muscle of women of the lower plasma PLP tertile, but this was not observed in gastrocnemius muscle or in men. We conclude that adequate dietary vitamin B6 is essential for maintaining carnosine in skeletal muscles of rats. Significantly lower soleus carnosine content among women close to PLP deficiency suggests that a similar phenomenon exists in the humans

Simplified procedures to compute earthquake-induced sliding and overturning displacements of retaining walls

特集2 耐震構造学研究グループ (ERS

Pengaruh Dimensi Benda Uji Terhadap Kuat Tekan Beton

Kuat tekan adalah karakteristik mekanik utama dari beton yang dapat diketahui melalui penelitian uji tekan di laboratorium terhadap benda uji. Baik dalam bentuk kubus ataupun silinder dengan ukuran standar: 10cm x 10cm x 10cm dan 15cm x 15cm untuk kubus dan 10cm x 20cm dan 15cm x 30cm untuk silinder. Untuk mendapatkan informasi mengenai kecendrungan harga kuat tekan beton dengan variasi dimensi benda uji, telah dilakukan penelitian-penelitian di laboratoriun untuk mendapatkan komposisi campuran tertentu pada umur beton 28 hari, variasi ukuran benda uji dibuat: 10cm x 10cm x 10cm, 12,5cm x 12,5cm x 12,5cm dan 15cm x 15cm x 15cm untuk kubus dan 10cm x 20cm, 12,5cm x 25cm dan 15cm x 30cm untuk silinder. Dengan jumlah benda uji masing-masing 20 buah untuk setiap ukuran benda uji. Melalui prosedur standar pengujian kuat tekan dan menggunakan formula-formula baku perhitungan tekan rata-rata diperoleh informasi bahwa peningkatan ukuran dimensi benda uji menghasilkan penurunan kuat tekan rata-rata, untuk benda uji kubus dengan ukuran masing-masing: 10cm x 10cm x 10cm, 12,5cm x 12,5cm x 12,5cm dan 15cm x 15cm x 15cm diperoleh kuat tekan rata-rata masing-masing: 32,86MPa, 31,26MPa dan 31,036MPa. Sedangkan untuk silinder dengan kururan 10cm x 20cm, 12,5cm x 25cm dan 15cm x 30cm diperoleh kuat tekan rata-rata masing-masing: 31,47MPa, 30,85MPa dan 30,44MPa

Vitamin B6 Prevents IL-1β Protein Production by Inhibiting NLRP3 Inflammasome Activation

Vitamin B6 includes six water-soluble vitamers: pyridoxal (PL), pyridoxamine (PM), pyridoxine (PN), and their phosphorylated forms. Pyridoxal 5o\u27-phosphate (PLP) is an important cofactor for many metabolic enzymes. Several lines of evidence demonstrate that blood levels of PLP are significantly lower in patients with inflammation than in control subjects and that vitamin B6 has anti-inflammatory effects, with therapeutic potential for a variety of inflammatory diseases. Although one of our group previously demonstrated that PL inhibits the NF-κB pathway, the molecular mechanism by which vitamin B6 suppresses inflammation is not well understood. Here, we showed that both PL and PLP suppressed the expression of cytokine genes in macrophages by inhibiting Toll-like receptor (TLR)-mediated TAK1 phosphorylation and the subsequent NF-κB and JNK activation. Furthermore, PL and PLP abolished NLRP3-dependent caspase-1 processing and the subsequent secretion of mature IL-1β and IL-18 in LPS-primed macrophages. In contrast, PM and PN had little effect on IL-1β production. PLP, but not PL, markedly reduced the production of mitochondrial reactive oxygen species (ROS) in peritoneal macrophages. Importantly, PL and PLP reduced IL-1β production induced by LPS and ATP, or by LPS alone, in mice. Moreover, PL and PLP protected mice from lethal endotoxic shock. Collectively, these findings reveal novel anti-inflammatory activities for vitamin B6 and suggest its potential for preventing inflammatory diseases driven by the NLRP3 inflammasome. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc

Molecular cloning of doublesex genes of four cladocera (water flea) species

BACKGROUND: The gene doublesex (dsx) is known as a key factor regulating genetic sex determination in many organisms. We previously identified two dsx genes (DapmaDsx1 and DapmaDsx2) from a freshwater branchiopod crustacean, Daphnia magna, which are expressed in males but not in females. D. magna produces males by parthenogenesis in response to environmental cues (environmental sex determination) and we showed that DapmaDsx1 expression during embryonic stages is responsible for the male trait development. The D. magna dsx genes are thought to have arisen by a cladoceran-specific duplication; therefore, to investigate evolutionary conservation of sex specific expression of dsx genes and to further assess their functions in the environmental sex determination, we searched for dsx homologs in four closely related cladoceran species. RESULTS: We identified homologs of both dsx genes from, D. pulex, D. galeata, and Ceriodaphnia dubia, yet only a single dsx gene was found from Moina macrocopa. The deduced amino acid sequences of all 9 dsx homologs contained the DM and oligomerization domains, which are characteristic for all arthropod DSX family members. Molecular phylogenetic analysis suggested that the dsx gene duplication likely occurred prior to the divergence of these cladoceran species, because that of the giant tiger prawn Penaeus monodon is rooted ancestrally to both DSX1 and DSX2 of cladocerans. Therefore, this result also suggested that M. macrocopa lost dsx2 gene secondarily. Furthermore, all dsx genes identified in this study showed male-biased expression levels, yet only half of the putative 5’ upstream regulatory elements are preserved in D. magna and D. pulex. CONCLUSIONS: The all dsx genes of five cladoceran species examined had similar amino acid structure containing highly conserved DM and oligomerization domains, and exhibited sexually dimorphic expression patterns, suggesting that these genes may have similar functions for environmental sex determination in cladocerans

Zinc-Complexes of Histidine and the Related Compounds in Aqueous Solution

Zinc is the constituent element of insulin and is an essential element for the function of some enzymes, such as carbonic anhydrase, carboxypeptidase and alcohol dehydrogenase. Deficiency of zinc in the media of the tissue culture of mammalian kidneys causes inhibition of the biosyntheses of thiamine kinase and deoxyribonucleic acid. On the other hand, most of the amino acids have an ability to form metal complexes. In food technology, the ability of amino acids as sequestering agents for transitional metal elements is applied to the prevention of the autoxidation of glycerides. Among numerous amino acids, histidine is of great interest because the imidazole group forms 7T-bonds with metal elements. Most of the researches on the zinc-histidine complexes so far published are concerned with equilibria in the complex formations 1 l-4 l or with crystallographic analyses of the complexes. sl 6 l Such results are not available for considering the biochemical roles of zinc and histidine. Know ledges wanted for understanding biochemical phenomena, such as an enzyme action or a protein denaturation are the effects of pH on the formation of zinc-histidine complexes in aqueous solution. Accordingly, the formation of zinc-complexes with histidine and the related compounds in aqueous solution are dealt with in this paper. MATERIALS AND METHODS Materials All the reagents used m this experiment were of guaranteed grade, and distilleddeionized water was used in the preparation of the various samples. A stock solution of ZnS04 was prepared so as to contain 1.8 or 3.6 X l0-3 M Zn and the Zn concentra