Factors underlying genotypic differences in the induction of photosynthesis in soybean [Glycine max (L.) Merr.]

Crop leaves are subject to continually changing light levels in the field. Photosynthetic efficiency of a crop canopy and productivity will depend significantly on how quickly a leaf can acclimate to a change. One measure of speed of response is the rate of photosynthesis increase toward its steady state on transition from low to high light. This rate was measured for seven genotypes of soybean [Glycine max (L.) Merr.]. After 10 min of illumination, cultivar ‘UA4805’ (UA) had achieved a leaf photosynthetic rate (P_n) of 23.2 μmol · m^?2 · s^?1, close to its steady‐state rate, while the slowest cultivar ‘Tachinagaha’ (Tc) had only reached 13.0 μmol · m^?2 · s^?1 and was still many minutes from obtaining steady state. This difference was further investigated by examining induction at a range of carbon dioxide concentrations. Applying a biochemical model of limitations to photosynthesis to the responses of P_n to intercellular CO₂ concentration (C_i), it was found that the speed of apparent in vivo activation of ribulose‐1:5‐bisphosphate carboxylase/oxygenase (Rubisco) was responsible for this difference. Sequence analysis of the Rubisco activase gene revealed single nucleotide polymorphisms that could relate to this difference. The results show a potential route for selection of cultivars with increased photosynthetic efficiency in fluctuating light.     

Abasic oligodeoxyribonucleoside phosphorothioates: synthesis and evaluation as anti-HIV-1 agents.

The syntheses and anti-HIV-1 evaluations of two, abasic oligodeoxyribonucleotide phosphorothioate analogs, d[Cps(Eps)26C] and d[Cps(Vps)26C] (where E and V derive from 1,2-dideoxy-D-ribofuranose and (+/-)-butane 1, 3-diol, respectively), are described.     

Extraction and purification of a new compound containing selenium and mercury accumulated in dolphin liver

Dolphins sometimes accumulate Hg and Se as high as 100 μg/g or more in their livers. In the present study, a compound containing Hg and Se in a dolphin liver was extracted and purified by cation exchange, gel filtration, and paper, anion exchange, and chelate chromatographies. The Hg and Se contents in every fraction were determined by atomic absorption spectrometry using the palladium addition method. In all chromatographic fractions Hg and Se appeared in the 1∶1 molar ratio. The purified compound is water-soluble, with a molecular weight of less than 1000, and contains amino-groups, as well as Hg and Se at a 1∶1 molar ratio. Mercury in the compound is not removed by the chelate resin, indicating that the metal is not ionic and is tightly bound.     

Structural and regulatory studies on the ribulose bisphosphate carboxylase-oxygenase of Anabaena cylindrica

Ribulose 1,5-bisphosphate (RuBP) carboxylase-oxygenase fromthe cyanobacterium Anabaena cylindrica has been purified tohomogeneity by the criterion of polyacrylamide gel electrophoresisand shown to consist of two types of subunits of molecular weights51K (large) and 12K (small). The enzyme is of the higher planttype and probably consists of 8 large plus small subunits. Isoelectricfocusing of the S-carboxymethylated protein in 8 M urea revealeda profile of consisting of 3 major polypeptides plus 1 minorpolypeptide. Some characteristics of the carboxylase and oxygenasereactions were studied using simultaneous measurements of bothactivities. Pyridoxal 5'-phosphate inhibited both activitiesequally. Neither the carboxylase nor oxygenase reaction wasaffected by glutamate (5 mM), although 6-phosphogluconate andfructose 1,6-bisphosphate inhibited both reactions. RuBP oxygenasewas more sensitive to 6-phosphogluconate (0.5 and 1.0 mM) thanRuBP carboxylase. Marked changes in the oxygenase to carboxylaseactivity ratio of the purified enzyme were effected by homologousantiserum (which preferentially inhibited carboxylation). ¹Present address: Institute of Applied Microbiology, Universityof Tokyo, Bunkyo-ku, Tokyo 113, Japan. (Received May 22, 1980; )     

Establishment of hypersensitive radioimmunoassay for islet amyloid polypeptide using antiserum specific for its N-terminal region.

Using a synthetic N-terminal hexadecapeptide of islet amyloid polypeptide (IAPP), we prepared an antiserum specific for IAPP[1-16] and established an extremely sensitive radioimmunoassay (RIA) for the peptide with a minimum detection level of 0.26 fmol/tube. Since the N-terminal sequence of IAPP is 100% conserved in many mammalian species, the RIA is widely applicable in quantifying their IAPP. Analyses of pancreatic extracts of human and hamster using reverse-phase high performance liquid chromatography coupled with the RIA revealed that almost all pancreatic IAPP consisted of IAPP[1-37]. On the other hand, rat and mouse pancreata contained substantial amounts of IAPP[1-16] and IAPP[1-17] in addition to IAPP[1-37] as a major molecular form. In human plasma, IAPP[1-37] is the major molecular form secreted into the circulation in response to glucose administration. The RIA established in this study is promising in elucidating the physiological functions and the pathophysiological significance of IAPP in diabetes mellitus.     

Relationsnip Between the Nutritive Value of Dietary Protein and Liver Xanthine Oxidase Activity in Young Rats

The relationship between the nutritive value of dietary protein and the activity of lievr xanthine oxidase in growing rats as related to the growth rate and the protein efficiency ratio has been investigated.

The response curve of liver xanthine oxidase plotted against the protein level in the diet was essentially exponential, and the lower portion of this curve was linear. The slope of this straight portion, i.e., the tangent of the curve was observed to reflect the quality of dietary protein from comparison with the growth rate and the protein efficiency ratio.     

Age-related decrease of urinary excretion of human epidermal growth factor (hEGF)

Epidermal growth factor (EGF) has been first isolated from the submandibular glands of the male mouse and recently from human urine. Despite its potent mitogenic effect in a variety of tissues, the physiological functions of EGF in human still remain undetermined. In order to study the effect of age on urinary human EGF (hEGF), we have evaluated urinary excretion of hEGF in normal subjects over a wide range of age (20–79 yr.) using homologous radioimmunoassay (RIA) for hEGF. Urinary excretion of hEGF expressed as a function of creatinine significantly decreased with increasing age, age, while females excreted significantly more hEGF than males. These data suggest that urinary excretion of hEGF decreases with age in normal subjects which may be due to reduced synthesis and/or secretion of hEGF.     

Design and synthesis of estrogen receptor degradation inducer based on a protein knockdown strategy

We designed and synthesized estrogen receptor (ER) degradation inducers 5, 6, and 7, which crosslink the ER and the cellular inhibitor of apoptosis protein 1 (cIAP1). Compounds 5, 6, and 7 induced cIAP1-mediated ubiquitylation of ERα resulting in its proteasomal degradation.     

Double protein knockdown of cIAP1 and CRABP-II using a hybrid molecule consisting of ATRA and IAPs antagonist

Protein knockdown can be achieved by the use of a small molecule that possesses affinity for both the target protein and ubiquitin ligase. We have designed such a degradation-inducing molecule targeting cIAP1 and CRABP-II, which are involved in proliferation of several cancer cell lines and in neuroblastoma growth, respectively. As a CRABP-II-recognizing moiety, all-trans retinoic acid (ATRA, 3), a physiological ligand of CRABP, was chosen. As a cIAP1-recognizing moiety, MV1 (5), which is a cIAP1/cIAP2/XIAP pan-ligand, was chosen. Although cIAP1 itself possesses ubiquitin ligase activity, we expected that its decomposition would be efficiently mediated by related molecules, including cIAP2 and XIAP, which also possess ubiquitin ligase activity. The designed degradation inducer 6, in which ATRA (3) and MV1 (5) moieties are connected via a linker, was synthesized and confirmed to induce efficient degradation of both cIAP1 and CRABP-II. It showed potently inhibited the proliferation of IMR32 cells.