Isolation, characterization, and mapping of the stay green mutant in rice.

Leaf color turns yellow during senescence due to the degradation of chlorophylls and photosynthetic proteins. A stay green mutant was isolated from the glutinous japonica rice Hwacheong- wx through N-methyl-N-nitrosourea mutagenesis. Leaves of the mutant remained green, while turning yellow in those of the wild-type rice during senescence. The stay green phenotype was controlled by a single recessive nuclear gene, tentatively symbolized as sgr(t). All the phenotypic characteristics of the mutant were the same as those of the wild-type lines except for the stay green trait. The leaf chlorophyll concentration of the mutant was similar to that of the wild-type before heading, but decreased steeply in the wild-type during grain filling, while very slowly in the mutant. However, no difference in photosynthetic activity was observed between the stay green mutant and the yellowing wild-type leaves, indicating that senescence is proceeding normally in the mutant leaves and that the mutation affects the rate of chlorophyll degradation during the leaf senescence. Using phenotypic and molecular markers, we mapped the sgr(t) locus to the long arm of chromosome 9 between RFLP markers RG662 and C985 at 1.8- and 2.1-cM intervals, respectively.

Spectrofluorimetric method for determination of aluminium with chromotropic acid and its application to water samples.

A rapid and sensitive method for the trace level determination of aluminium based on the formation of a 1:1 complex with chromotropic acid (1,8-dihydroxynaphthlene-3,6-disulfonic acid) in an methanol medium is reported. The fluorescence intensity of the system was 50 times greater than that of the system without aluminium. This method is very sensitive and selective for the direct determination of aluminium ion. The fluorescence is excited at 346 nm and measured at 370 nm. The optimum conditions are a chromotropic acid concentration of 5.0 ml (1.0x10(-4) M) and pH 4.0+/-0.5 (acetic acid-sodium acetate buffer). The fluorescence intensity is a linear function of the concentration of Al(III) in the range 2-100 ng ml(-1) and the detection limit is 1.0 ng ml(-1). The method has been applied successfully to the determination of trace amount of Al(III) in tap, river and sea-water samples.

Simultaneous determination of trace uranium(VI) and zinc(II) by adsorptive cathodic stripping voltammetry with aluminon ligand.

Uranium(VI) complexed with aluminon (3-[bis(3-carboxy-4-hydroxy-phenyl)methylene]-6-oxo-1,4-cyclohexadiene-1-carboxylic acid triammonium salt) was determined by adsorptive cathodic stripping voltammetry (ACSV) using a hanging mercury drop electrode. Trace uranium(VI) and zinc(II) can be simultaneously determined in a single scan in the presence of aluminon and urea. Optimal conditions were found to be: accumulation time; 180-200 s, accumulation potential; 50 mV versus Ag/AgCl, scan rate; 40 mV s(-1), supporting electrolyte; 0.1 M sodium acetate buffer at pH 6.5-7.0, and concentration of aluminon; 1x10(-6) M. The linear range of uranium(VI) and zinc(II) were observed over the concentration range 2-33 and 30-120 ng ml(-1), respectively. The detection limit (S/N=3) are 0.2 ng ml(-1) (uranium) and 30 ng ml(-1) (zinc). A good reproducibility shows RSDs of 2.5-4.0% (n=10). The procedure offers high selectivity, with the presence of urea masking some metal ions.

Spectrophotometric determination of trace amounts of cobalt with 2-hydroxybenzaldehyde-5-nitro-pyridylhydrazone in presence of surfactant after separation with Amberlite IRC-718 resin.

2-Hydroxybenzaldehyde-5-nitro-pyridylhydrazone (2HB-5NPH) was synthesized and its application in the spectrophotometric determination of metal ions was studied in the presence of surfactants. A separation procedure, using a short column filled with Amberlite IRC 718, is proposed for the spectrophotometric determination of traces of cobalt. The influence of several ions, as interference, was discussed. The procedure was applied to determination of cobalt in mixture sample with satisfactory results (>/=recovery 96%; relative error

Determination of iron(III) with salicylic acid by the fluorescence quenching method.

The spectrofluorimetric determination of Fe(3+) using salicylic acid as an emission reagent has been investigated by measuring the decrease of fluorescence intensity of salicylic acid due to the complexation of Fe(3+)-salicylic acid. An emission peak of salicylic acid, which is decreased linearly by addition of Fe(3+), occurs at 409 nm in aqueous solution with excitation at 299 nm. The determination of the ferric ion is in the range 1x10(-6)-10x10(-6) M Fe(3+) (0.0558-0.558 mug/ml) and the detection limit is 5x10(-8) M. The quenching effect of Fe(3+) on the fluorescence intensity of salicylic acid may be considered on the basis of complexation between salicylic acid and Fe(3+). The effects of foreign ions were investigated.

Spectrofluorimetric determination of iron(III) with 2-pyridinecarbaldhyde-5-nitro-pyridylhydrazone in the presence of hexadecyltrimethylammonium bromide surfactant.

2-pyridinecarbaldehyde-5-nitro-pyridylhydrazone (2PC-5NPH) was synthesized and its application in the spectrofluorimetric determination of Fe(III) ions in the presence of surfactants was examined. An emission peak of 2PC-5NPH, which increased remarkably by the addition of Fe(III), occurs at 420 nm upon excitation at 300 nm, and allows for the sensitive, selective determination of the ferric ion in the 0.20-1.45 mug ml(-1) range. The detection limit is 0.028 mug ml(-1) in the presence of hexadecyltrimethylammonium bromide (CTMAB).

Isolation and characterization of GTP cyclohydrolase I from mouse liver. Comparison of normal and the hph-1 mutant.

GTP cyclohydrolase I, an enzyme that catalyzes the first reaction in the pathway for the biosynthesis of pterin compounds, was purified from of C3H mouse liver by 192-fold to apparent homogeneity, using Ultrogel AcA34, DEAE-Trisacryl, and GTP-agarose gels. Its native molecular weight was estimated at 362,000. When the enzyme was subjected to electrophoresis on a denaturing polyacrylamide gel, only one protein band was evident, and its molecular weight was estimated at 55,700. The NH2-terminal amino acid of this enzyme was serine. These results indicate the enzyme consists of six to eight subunits. No coenzyme or metal ion was required for activity. This enzyme activity was inhibited by most of divalent cations and was slightly activated by potassium ion. The Km value for GTP was determined to be 17.3 microM. The temperature and pH optima for the activity were 60 degrees C and pH 8.0-8.5, respectively. The expected products, a dihydroneopterin compound and formic acid, were found in a molar ratio of 1.01. A polyclonal antiserum generated against the purified enzyme was used to compare GTP cyclohydrolase I from the hph-1 mutant and normal mouse. The hph-1 mutant liver contained only 8% of normal specific activity, but a normal amount of GTP cyclohydrolase I antigen as compared with the C3H mouse. Subunit molecular weight and electrophoretic behavior of GTP cyclohydrolase I from hph-1 mutant were not different from those of the enzyme from C3H mouse. These results suggest that the hph-1 mutation may involve alteration of the catalytic site but does not detectably alter the whole enzyme structure.