紫外分光光度法测定甘草黄酮含量

采用分光光度法,测定了甘草中总黄酮的合量,检测波长为500nm,标准曲线相关系数R^2为0．9994,相对标准偏差为0．20％,平均加样回收率为100．20％。结果表明,此法准确度较高,为甘草生药及成品药中甘草黄酮合量测定提供了一种切实可行的方法     

变色酸-分光光度法测定丝氨酸含量

建立了变色酸-分光光度法测定丝氨酸含量的方法。丝氨酸在一定的pH条件下经高碘酸钠氧化后能与变色酸发生发应,产物在570 nm处有最大吸光值,且吸光值与丝氨酸的含量呈一次线性关系。结果表明,丝氨酸在0-1.0 g.L-1范围内呈良好的线性关系(r=0.9973),平均加样回收率为100.30%,RSD为1.11%。将测量结果与高效液相测量结果做比较,两种方法的相符率达到99%至101%。变色酸-分光光度法操作简便,结果准确。     

分光光度法测定豆类及其粗蛋白质中的色氨酸

建立一种快速、准确测定各种豆类试样及粗蛋白质中的色氨酸含量的分光光度法讨论最佳试验条件及试剂用量,反应物在410nm处具有最大吸收波长ε=1.103×104L·mol-1·cm-1,回收率93.50-110.20%,相对标准偏差RSD＜2.61.     

紫外可见分光光度法测定杜仲绿原酸含量的方法研究

目前,测定绿原酸含量的方法很多,常采用毛细管电泳法、ＨＰＬＣ法、可见分光光度法和纸层析-紫外可见分光光度法等[1,2,3,4]。但样品处理均采用索氏回流提取,后经层析分离洗脱等步骤,时间长、效率低。本文采用紫外可见分光光度法测定绿原酸含量,只需超声波提取一小时,不经...     

蒽酮分光光度法测定海藻多糖总糖含量

本文报道了在室温下用蒽酮分光光度法测定海藻多糖总糖的含量,本法总糖测定的回收率９７．５％－１０３％,标准偏差０．３。本法设备简便,迅速、准确。     

分光光度法测定地骨皮中牛磺酸含量

用分光光度法测定地骨皮中是否含有牛磺酸。在一定条件下,牛磺酸与乙酰丙酮和甲醛反应生成带色的配合物,建立了测定牛磺酸含量的分光光度法。结果表明,地骨皮中含有牛磺酸,已测定样品1中牛磺酸的质量分数为3.124 mg.g-1,样品2中牛磺酸的质量分数为6.203 mg.g-1,且样品2中的牛磺酸质量分数极显著高于样品1(p<0.01)。研究结果表明,地骨皮中含有牛磺酸,而且分光光度法成本低,干扰少,是测定地骨皮中牛磺酸质量分数的较好方法。     

紫外分光光度法测定甘草黄酮含量

采用分光光度法,测定了甘草中总黄酮的含量,检测波长为500 nm,标准曲线相关系数R²为0.9994,相对标准偏差为0.20%,平均加样回收率为100.20%。结果表明,此法准确度较高,为甘草生药及成品药中甘草黄酮含量测定提供了一种切实可行的方法。     

分光光度法测定灵芝三萜含量的干扰因素探讨

根据药典方法,以齐墩果酸为对照品,对灵芝中含有的三萜、甾醇和脂肪酸3种类型化合物进行分光光度法测定,并对影响三萜含量测定的因素进行分析。结果表明灵芝中的甾醇和脂肪酸类化合物会干扰所有的测定结果,尤其影响灵芝孢子中三萜含量的测定。灵芝子实体中三萜化合物的结构特征,造成了其测定值远远低于真实值。因此,分光光度法不适用于测定灵芝子实体、菌丝体和孢子及其相关产品中的三萜含量。     

紫外分光光度法测定肉碱转化液中巴豆甜菜碱的含量

通过对巴豆甜菜碱和L－肉碱在紫外188－215mm的光吸收的比较,建立了紫外分光光度法测定肉碱转化液中巴豆甜菜碱含量的方法,测定波长205mm,线性范围0－25ug/ml,该方法快速方便 ,重复性好,可用于L－肉碱生产过程中巴豆甜菜碱的跟踪检测。     

分光光度法测定苦参中微量元素铜的含量

采用分光光度法测定了苦参中微量元素铜的含量,探讨了测定条件,并与火焰原子吸收光度法进行了对比。结果表明,两种方法的测定结果吻合,平均回收率分别为95.2%和101.6%,相对标准偏差分别为1.82%和1.10%,结果可靠,特别是分光光度法仪器价格低,操作简便,适用范围广,可用于实际样品的测定。     

Hypothesis for the evolution of three-helix Chl a/b and Chl a/c light-harvesting antenna proteins from two-helix and four-helix ancestors

The nuclear-encoded Chl a/b and Chl a/c antenna proteins of photosynthetic eukaryotes are part of an extended family of proteins that also includes the early light-induced proteins (ELIPs) and the 22 kDa intrinsic protein of PS II (encoded by psbS gene). All members of this family have three transmembrane helices except for the psbS protein, which has four. The amino acid sequences of these proteins are compared and related to the three-dimensional structure of pea LHC II Type I (Kühlbrandt and Wang, Nature 350: 130–134, 1991). The similarity of psbS to the three-helix members of the family suggests that the latter arose from a four-helix ancestor that lost its C-terminal helix by deletion. Strong internal similarity between the two halves of the psbS protein suggests that it in turn arose as the result of the duplication of a gene encoding a two-helix protein. Since psbS is reported to be present in at least one cyanobacterium, the ancestral four-helix protein may have been present prior to the endosymbiotic event or events that gave rise to the photosynthetic eukaryotes. The Chl a/b and Chl a/c antenna proteins, and the immunologically-related proteins in the rhodophytes may have had a common ancestor which was present in the early photosynthetic eukaryotes, and predated their division into rhodophyte, chromophyte and chlorophyte lineages. The LHC I-LHC II divergence probably occurred before the separation of higher plants from chlorophyte algae and euglenophytes, and the different Types of LHC I and LHC II proteins arose prior to the separation of angiosperms and gymnosperms.Abbreviations CAB Chl a/b-binding - ELIP early light-induced protein - FCP fucoxanthin-Chl a/c protein - PCR polymerase chain reaction - TMH trans-membrane helix     

Changes in Chlorophyll a/b Ratio and Products of CO(2) Fixation by Algae Grown in Blue or Red Light

Chlamydomonas and Chlorella were grown for 10 days in white light. 955 μw/cm² blue light (400-500 mμ) or 685 μw/cm² red light (above 600 mμ). Rates of growth in blue or red light were initially slow, but increased over a period of 5 days until normal growth rates were reestablished. During this adaptation period in blue light, total chlorophyll per volume of algae increased 20% while the chlorophyll a/b ratio decreased. In red light no change was observed in the total amount of chlorophyll or in the chlorophyll a/b ratio. After adaptation to growth in blue light and upon exposure to ¹⁴CO₂ with either blue or white light for 3 to 10 minutes, 30 to 36% of the total soluble fixed ¹⁴C accumulated in glycolate-¹⁴C which was the major product. However, with 1 minute experiments, it was shown that phosphate esters of the photosynthetic carbon cycle were labeled before the glycolate. Glycolate accumulation by algae grown in blue light occurred even at low light intensity. After growth of the algae in red light, ¹⁴C accumulated in malate, aspartate, glutamate and alanine, whereas glycolate contained less than 3% of the soluble ¹⁴C fraction.     

Conversion of Chlorophyll b to Chlorophyll a and the Assembly of Chlorophyll with Apoproteins by Isolated Chloroplasts

The photosynthetic apparatus is reorganized during acclimation to various light environments. During adaptation of plants grown under a low-light to high-light environment, the light-harvesting chlorophyll a/b-protein complexes decompose concomitantly with an increase in the core complex of photosystem II. To study the mechanisms for reorganization of photosystems, the assembly of chlorophyll with apoproteins was investigated using isolated chloroplasts. When [14C]chlorophyllide b was incubated with chloroplasts in the presence of phytyl pyrophosphate, it was esterified and some of the [14C]chlorophyll b was converted to [14C]chlorophyll a via 7-hydroxymethyl chlorophyll. [14C]Chlorophyll a and b were incorporated into chlorophyll-protein complexes. Light-harvesting chlorophyll a/b-protein complexes of PSII had a lower [14C]chlorophyll a to [14C]chlorophyll b ratio than P700-chlorophyll a-protein complexes, indicating the specific binding of chlorophyll to apoproteins in our systems. 7-Hydroxymethyl chlorophyll, an intermediate molecule from chlorophyll b to chlorophyll a, did not become assembled with any apoproteins. These results indicate that chlorophyll b is released from light-harvesting chlorophyll a/b-protein complexes of photosystem II and converted to chlorophyll a via 7-hydroxymethyl chlorophyll in the lipid bilayer and is then used for the formation of core complexes of photosystems. These mechanisms provide the fast, fine regulation of the photosynthetic apparatus during construction of photosystems.     

Isolation of Crystalline Water-soluble Chlorophyll Proteins with Different Chlorophyll a and b Contents from Stems and Leaves of Lepidium virginicum

Two types of water-soluble chlorophyll proteins were isolatedfrom Lepidium virginicum L. grown in Japan. The protein isolatedfrom the leaves (CP663L) had a low chlorophyll a/b ratio (1.5–1.7),and that from the stems (CP663S) had a high ratio (3.4–3.5).CP663S showed the same crystal forms and almost the same molecularweight and subunit composition as CP663I. (Received October 26, 1981; Accepted February 4, 1982)     

分光光度法测定金荞麦(-)-表儿茶素含量的方法研究

为建立香荚兰素-盐酸分光光度法对表儿茶素含量的测定方法,实验分别以乙醇和水作溶剂,在34.79～208.74μg范围内取样置50 mL容量瓶测定,结果发现:①以乙醇作溶剂时,测定波长为508 nm,1%香荚兰浓盐酸添加量应超过40mL(CV≤1.86%),测定时间以40 min后为宜(CV≤2.65%),标准曲线线性关系(R=0.999 3)与精确度(CV=2.66%)、准确度(P0.05)良好。②以水作溶剂时,测定波长为504 nm,显色反应不稳定,标准曲线线性关系(R=0.988 1)也较一般。③采用乙醇作溶剂时,测得金荞麦块根中(-)-表儿茶素类物质含量占干物质的2.22%(CV≤3.90%),该法操作简便,灵敏度高,重现性好。     

Chlorophyll b-Deficient Mutants of Rice: I. Absorption and Fluorescence Spectra and Chlorophyll a/b Ratios

Absorption spectra and their fourth derivatives of chloroplastsisolated from 16 different rice chlorina mutants were determinedat liquid nitrogen temperature. The results suggest that Chlb is absent from 10 mutants labelled chlorina-1 to -10, while6 mutants named chlorina-11 to -16 contain low levels of Chlb. Low temperature fluorescence emission spectra indicate thata light-harvesting Chl a/b protein of photosystem I is presentin chlorina-11 to -16 but not in chlorina-1 to -10. Reinvestigationof Chl a/b ratios by a sensitive fluorescence method shows thatthe 16 mutants are divided into three groups different in thedegree of Chl b-deficiency; chlorina-1 to -10 totally lack Chlb (Type I), chlorina-11 to -13 have Chl a/b ratio of about 10(Type II-A) and chlorina-14 to -16 have the ratio of about 15(Type II-B). (Received June 6, 1985; Accepted August 6, 1985)     

Organization of Chlorophyll a in the Light-Harvesting Chlorophyll a/b Protein Complex as Shown by Circular Dichroism : Liquid Crystal-Like Domains

The development of thylakoid stacking, accumulation of the light-harvesting chlorophyll a/b protein complex (LHCP), and the changes of circular dichroism (CD) which reflect the organization of chlorophyll molecules in greening thylakoids of bean Phaseolus vulgaris cv Red Kidney leaves were investigated.

Chloroplasts formed under intermittent light contained large double sheets of membrane with extensive appression in addition to separate lamellae. Thylakoids of such chloroplasts were devoid of LHCP and exhibited a relatively small CD in the chlorophyll absorption region. Upon continuous illumination, the rearrangement of membranes to characteristic grana and the accumulation of the LHCP was accompanied by the gradual appearance of the very intense CD signal with peaks at 682 to 684 (+) and 665 to 672 nanometers (−). The magnitude of differential absorption was approximately 100 times larger than that of the chlorophyll a in solution. This suggests a superhelical liquid crystal-like organization for LHCP, a texture which can be altered by changes of the electric field in the photosynthetic membranes.

     

Synthesis and Breakdown of the Apoproteins of Light-Harvesting Chlorophyll a/b Proteins in Chlorophyll b-deficient Mutants of Rice

Turnover, in the light, of apoproteins of light-harvesting chlorophylla/6-proteins for Photo-system I and II (LHC-I and LHC-II, respectively)was studied with the wild-type and three chlorophyll 6-deficientmutants of rice. (1) Synthesis of the 24 and 25 kDa apoproteinsof LHC-II and the 20 and 21 kDa apoproteins of LHC-I was examinedby incubating leaf segments with [³⁵S]-methionine. The threerice mutants, chlorina 2, which totally lacks chlorophyll b,and chlorina 11 and 14, which are partially deficient in chlorophyllb, synthesized the apoproteins as rapidly as did the wild typerice. (2) Pulse-chase experiments showed that breakdown of theapoproteins proceeded slowly, such that only a small proportionof the newly synthesized apoproteins was lost during the 48h of the chase in normal rice leaves. By contrast, large fractionsof the labelled apoproteins were rapidly degraded within thefirst several hours of the chase period in the chlorina mutants.The greater the deficiency in chlorophyll b of the mutant, thelarger were the rate and extent of the protein breakdown. Thisresult indicates that chlorophyll b is needed to stabilize theapoproteins of LHC-II and LHC-I. (3) However, even in chlorina2, there were small fractions of the apoproteins with lifetimesas long as those of apoproteins in the wild-type rice, suggestingthat the newly synthesized apoproteins are partially protectedby a factor(s) other than chlorophyll b. (4) The rate of turnoverof the apoproteins was significantly reduced in the dark andstrongly inhibited by prior treatment of leaf segments withchloramphenicol. (Received November 24, 1988; Accepted March 17, 1989)     

Migration of Electronic Energy from Chlorophyll b to Chlorophyll a in Solutions

Absorption, emission, and fluorescence excitation spectra of pure solutions of chlorophyll a (Chl a) and chlorophyll b (Chl b) in diethyl ether and of equimolecular mixed solutions of the two pigments, were determined at room temperature as functions of concentration (in the range from 5 × 10^-6 M to 4 × 10^-3 M) and of wavelength of the exciting light (in the regions 380-465 and 550-650 nm). The efficiency of energy transfer from Chl b to Chl a, derived from these data, was found to depend on the wavelength of exciting light. Furthermore, the transfer efficiency calculated from sensitization of Chl a fluorescence by Chl b was substantially smaller than that calculated from quenching of Chl b fluorescence by Chl a. Both these effects are tentatively explained as evidence of superposition of a “fast” energy transfer (taking place before the Boltzmann distribution of vibrational energy had been reached) upon the “delayed” transfer, which takes place after vibrational equilibration. The first-named mechanism is made possible by overlapping of the absorption bands of the two pigments; the second, by overlapping of the emission band of Chl b and the absorption band of Chl a. The first mechanism can lead to repeated transfer of excitation energy between pigment molecules, the second only to a one-time transfer from the donor to the acceptor. Both mechanisms could be of the same, second-order type, with the transfer rate proportional to r^-6. An alternative is for the fast mechanism to be of the first order, with the transfer rate proportional to r^-3, but spectroscopic evidence seems to make this alternative less probable.