Ion‐Exchange and Adsorption of Fe(III) by Sepia Melanin

Sepia eumelanin is associated with many metal ions, yet little is known about its metal binding capacity and the chemical nature of the binding site(s). Herein, the natural concentrations of metal ions are presented and the ability to remove metals by exposure of the melanin granules to EDTA is quantified. The results reveal that the binding constants of melanin at pH 5.8 for Mg(II), Ca(II), Sr(II) and Cu(II) are, respectively, 5, 4, 14 and 34 times greater than the corresponding binding constants of these ions with EDTA. By exposing Sepia eumelanin to aqueous solutions of FeCl₃, the content of bound Fe(III) can be increased from a natural concentration of ～180 ppm to a saturation limit of ～80 000 ppm or 1.43 mmol/g of melanin. Similar saturation limits are found for Mg(II) and Ca(II). Exposure of Sepia melanin granules to aqueous solutions containing Ca(II) results in the stoichiometric replacement of the initially bound Mg(II), arguing that these two ions occupy the same binding site(s) in the pigment. The pH‐dependent binding of Mg(II) and Ca(II) suggests coordination of these ions to carboxylic acid groups in the pigment. Mg(II) and Ca(II) can be added to a Fe(III)‐saturated melanin sample without affecting the amount of Fe(III) pre‐adsorbed, clearly establishing Fe(III) and Mg(II)/Ca(II) occupy different binding sites. Taking recent Raman spectroscopic data into account, the binding of Fe(III) is concluded to involve coordination to o‐dihydroxyl groups. The effects of metal ion content on the surface morphology were analyzed. No significant changes were found over the full range of Fe(III) concentration studied, which is supported by the Brunauer–Emmett–Teller surface area analysis. These observations imply the existence of channels within the melanin granules that can serve to transport metal ions.     

金乌贼墨汁营养成分分析及评价

采用氨基酸自动分析仪、原子吸收仪、液相色谱及常规化学分析法对金乌贼(Sepia esculenta)墨汁的基本营养组分以及氨基酸、矿物质元素、维生素的组成和含量进行了测定。在所检测的17种氨基酸中,含有7种必需氨基酸和2种半必需氨基酸。同时富含Mg、Ca、K、Na等常量矿物元素以及Fe、sr、Al等微量元素和脂溶性、水溶性维生素。     

商陆毛状根的诱导、培养及其扼甙的产生

发根农杆菌（Agrobacterium rhizogenes）R1601感染商陆叶片外植体1周后,在其切口处产生毛状根,20d后产生毛状根的外植体比例达70%,毛状根可直接从叶片外植体叶脉处或从叶脉处产生的愈伤组织上产生,毛状根能在无激素的MS培养基上自主生长,其呼吸速率比对照根提高85.6%,冠瘿碱检测和PCR扩增结果表明,发根农杆菌RiT-DNA的冠瘿碱合成酶基因及其Ri质粒的rol基因均已在商陆毛状根基因组中得到表达。毛状根中总皂甙含量约为自然根的1.54倍,但其多糖含量则仅为非转化根的70%。     

木薯的组织培养和基因转化

木薯是重要的热带作物之一, 其块根富含淀粉, 是热带、亚热带地区近５ 亿人粮食的主要来源。简单介绍近年来运用生物技术改良木薯的研究进展。     

Using microsatellites,isozymes and AFLPs to evaluate genetic diversity and redundancy in the cassava core collection and to assess the usefulness of DNA-based markers to maintain germplasm collections

The cassava core collection was selected to represent, with minimum repetitiveness, the potential genetic diversity of the crop. The core (630 accessions) was chosen from the base collection (over 5500 accessions) on the basis of diversity of origin (country and geographic), morphology, isozyme patterns and specific agronomic criteria. To asses the genetic diversity of the core, 521 accessions were typed with four microsatellite loci. Allele diversity and frequency, and size variance of dinucleotide repeats (Rst statistic) were estimated. Microsatellite allele numbers and frequencies varied among countries: Colombia and Brazil had the largest number of different alleles across all loci. Mexico also had a high number, ranking fifth after Peru, Costa Rica and Venezuela (which tied). Unique alleles were present in accessions from Brazil, Colombia, Guatemala, Venezuela and Paraguay. A small number (1.34%) of potential duplicates were identified through isozyme and AFLP profiles. Thus, the present results indicated that traditional markers have been highly effective at selecting unique genotypes for the core. Future selections of cassava germplasm sets can be aided by DNA-based markers to ensure genetically representative, non-redundant samples. This revised version was published online in June 2006 with corrections to the Cover Date.     

Study on the factors affecting storage of edible aroids

The effects of temperature (15 °C, 25 °C, 30°C and 24–29°C), relative humidity (45%, 85% and 86–98%) and harvest maturity on the storage behaviour of cormels of the edible aroid species Colocasia esculenta and Xanthosoma sagittifolium were studied. The changes monitored were respiration rates, weight losses, incidence of decay and sprouting. Post-harvest losses that occurred during storage were influenced by the storage conditions, the state of maturity at harvest and the morphological characteristics of the cormels. When stored under high temperature and humidity more sprouting and decay occurred with C. esculenta cormels than with X. sagittifolium cormels. Less sprouting and decay occurred with Colocasia cormels at high temperature and low humidity than at high temperature and high humidity but higher weight losses were recorded. Wound pathogens were the major cause of post-harvest deterioration in Colocasia cormels and the causal pathogen of cormel decay was Sclerotium rolfsii. Under conditions of low temperature (15 °C) and high humidity (85%), cormels of both C. esculenta and X. sagittifolium were successfully stored for periods of 5–6 weeks. Similar storage periods were also possible under tropical ambient conditions with the Xanthosoma cultivars used in these experiments. Under the same storage conditions up to 60% decay occurred in the Colocasia cormels indicating the need for post-harvest fungicide treatment.     

萱草属有毒植物的研究

萱草属中某些种的根含神经性毒物,家畜采食或饲喂实验动物能引起中毒病的发生。在鉴于此对北萱草,黄花菜,北黄花菜,小黄花菜进行了植物调查鉴定及有毒成分—萱草根素的提取分离与毒性和结构再鉴定的研究,确认除黄花菜根外其它３种均含有萱草根素。讨论了黄花菜种鉴定中存在的问题。     

BLUE LIGHT PHOTOREACTIVATION IN ULTRAVIOLET-IRRADIATED YOUNG SPOROPHYTES OF ALARIA ESCULENTA AND LAMINARIA SACCHARINA (PHAEOPHYTA)1

Exposure of ultraviolet (UV)-irradiated young sporophytes of Alaria esculenta (L.) Grev. and Laminaria saccharina (L.) Lamour. to visible light resulted in recovery from UV damage that would otherwise cause much higher mortality. For this photoreactivation, blue light was highly effective, whereas negligible reactivation was produced in green or red light. The blue quantum requirements for a 50% response were 1.9 mol·m^?2 in A. esculenta and 1.2 mol·m^?2 in L. saccharina, which were comparable to those reported for other blue light responses requiring high energy found in brown algae.     

Water stress-induced alterations in the proline metabolism of drought-susceptible and -tolerant cassava (Manihot esculenta) cultivars

The free proline levels and activities of ornithine aminotransferase (EC 2.6.1.13) and proline oxidase (EC 1.5.2.2), two of the enzymes involved in proline metabolism were studied during the induction of water stress in a drought susceptible (M-4) and a drought tolerant (S-1315) cultivar of cassava ( Manihot esculenta Crantz). Water stress induced by polyethylene glycol (MW 6000, osmotic potential — 1.65 MPa) caused a ca 25-fold increase in proline in young excised leaves of the susceptible cultivar (M-4) while the increase was about 9-fold in the tolerant cultivar (S-1315). The activity of ornithine aminotransferase (OAT), a key enzyme involved in the biosynthesis of proline, was found to increase 3-fold in water stressed leaves of M-4 and about 2-fold in those of S-1315. The activity of proline oxidase, which is involved in the degradation of proline to pyrroline-5-carboxylate, was reduced by 50% in M-4 and nearly 25% in S-1315 on water stress. Comparison of the kinetic properties of OAT showed that the enzyme from water-stressed leaves is more stable to heat inactivation compared to that of control. These results indicate that during water stress there are alterations in the metabolism of proline in cassava, and the extent of alteration varies between drought-susceptible and -tolerant cultivars.