Purification of Photosystem II particles from Phormidium laminosum using the detergent dodecyl-β-d-maltoside. Properties of the purified complex

The purification and properties of a new oxygen-evolving Photosystem (PS) II particle from the thermophilic blue-green alga Phormidium laminosum are described. The activity of the lauryldimethylamine N-oxide PS II-enriched supernatant described previously (Stewart, A.C. and Bendall, D.S. (1979) FEBS Lett. 107, 308–312) was found to be stabilized for several days at 4°;C by the addition of a second detergent, dodecyl-β-d-maltoside (lauryl maltoside). The lauryl maltoside/lauryldimethylamine N-oxide extract could be fractionated by sucrose density gradient centrifugation. Very high rates of oxygen evolution, typically 1900–2400 μmol O₂/mg chlorophyll a per h at pH 7 with dimethylbenzoquinone and ferricyanide as acceptors, were observed for the lowest green band from the gradient. This fraction contained cytochromes b-559 (high-potential) and c-549, but was completely devoid of P-700 and cytochromes b-563 and f. The purified oxygen-evolving particles comprised seven major polypeptides (M_r 58 900, 52 400, 43 200, 33 900, 30 000, 16 000 and 15 000) and approximately five minor polypeptides. The particles contained 3–4 Mn atoms per reaction centre and had a chlorophyll antenna of approx. 50 chlorophyll a. The fast phase of fluorescence induction curves in the presence of hydroxylamine and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) could be described by an exponential, suggesting that no energy transfer was occurring between the PS II units responsible for this phase. Comparison of the area above the fluorescence induction curves in the absence and presence of DCMU suggested an acceptor pool size of 2–3 equivalents per centre.     

Production and HPLC analysis of black tea theaflavins and thearubigins during in vitro oxidation

A model fermentation system has been designed which utilizes pure catechins and partially purified polyphenol oxidase (EC 1.14.18.1 from green tea shoots. HPLC analysis of the products formed during in vitro oxidation has demonstrated a close similarity between this system and in vivo oxidation occurring during factory fermentation. Furthermore, changes in theaflavin and thearubigin levels, revealed by time courses of fermentation, show in vitro and in vivo systems to be qualitatively similar, although the former system produces considerably higher levels of both components. The model fermentation system, therefore, appears to be a suitable experimental system for studying the formation of theaflavin and thearubigin pigments under strictly controlled conditions. In preliminary experiments the theaflavins have been identified on HPLC profiles by enzymic oxidation of the relevant catechin pairs. Similarly, major coloured components other than theaflavins, which are considered to be thearubigins, have been shown to be formed by the oxidation and reaction of two gallocatechins (epigallocatechin and epigallocatechin gallate). The model fermentation system, in conjunction with HPLC as described in this paper, provides a means whereby precise data on theaflavin and thearubigin formation can be obtained and, in the case of the thearubigins, one which could yield additional structural information.     

An automatic system to study the responses of respiration and photosynthesis by submerged macrophytes to environmental variables

An apparatus to measure the rates of respiration and photosynthesis of aquatic plants in water at velocities of up to 200 mm s^–1 in a closed water-flow system with partial recirculation, is described. The temperature, the light regime and the concentration of dissolved oxygen are controlled automatically. Typical results are given for Ranunculus penicillatus var. calcareus which were repeatable between the same season in different years and compared with published data.     

Optimizing development time in a seasonal environment: The ‘ups and downs’ of clinal variation

Summary This paper explores the problem of adapting development time to changes in the length of time conditions are favourable for growth and reproduction (season length). It is shown that systematic changes in season length along some gradient such as latitude can generate either simple clines in development time or saw-tooth clines. The relationship between development time and body size gives rise to a corresponding variation in body size. The generation of a saw-tooth cline does not require sharp environmental changes. Both types of clinal variation are observed in insects.     

A comparative study of specific chromatic adaptation of the wildtype and trp mutant of Drosophila melanogaster

The trp mutant of Drosophila melanogaster was re-examined and compared with the wildtype using monochromatic blue and orange light to manipulate the bi-stable visual pigment states in the peripheral retinula cells R1-6 of white-eyed flies. Recovery of sensitivity by application of orange light either during or after blue-adaptation is different in w;trp flies from that in bw;cn flies and does not proceed as predicted from the trp genotype. Blue-adaptation by isolating the activity of the central retinula cells confirms that the trp lesion affects these receptors also.     

Pathophysiology of post-gastrectomy hypoglycaemia

The blood glucose and plasma insulin response to oral glucose and slow intravenous infusion of glucose was determined in seven patients who had undergone partial gastrectomy or gastroenterostomy. Similar studies were conducted in normal subjects; in these experiments oral glucose administration was replaced by infusion of glucose direct into the jejunum in order to simulate the rapid gastric emptying which occurs after gastric surgery.Peak insulin levels were much higher after oral or intrajejunal glucose, though peak blood glucose levels were higher after intravenous glucose. Despite the high insulin levels occurring with oral administration the late fall in blood glucose below fasting levels was not significantly greater after oral or intrajejunal glucose than after intravenous administration of the sugar. This does not support the concept that hyperinsulinaemia alone is responsible for reactive hypoglycaemia.     

Derivatives of 6-deuterio-D-glucose,absolute configuration at C-6, and steric disposition of an acetoxymethyl group

Arabinoxylan preparations from sugar cane show temperature-induced shifts of optical rotation in aqueous methyl sulphoxide solution, the sign and magnitude of which depend on the content of arabinofuranose side-groups. The shift has a sigmoidal form and shows a distinct hysteresis loop on heating and cooling. This evidence, together with the sign and magnitude, is interpreted in terms of a conformation change of the backbone of β-(1→4)-linked D-xylose residues, from the random coil to an ordered, ribbon-like conformation similar to that which is known to exist in the solid state. The driving force for this change is not intramolecular but derives from an aggregation that occurs simultaneously and can be detected by other methods. The arabinofuranose side-groups can be incorporated into the ordered assembly and contribute to the optical rotation shift, and they therefore have an unusual role compared with other polysaccharide side-chains. We conclude that the optical rotation shifts show a “melting” and re-formation of ordered associations which may imitate the natural biological cohesion between hemicellulose chains.     

Biosynthesis of geraniol and nerol and their β-d-glucosides in Perlargonium graveolens and Rosa dilecta

1. 3R-[2-(14)C]Mevalonate was incorporated into geranyl and neryl beta-d-glucosides in petals of Rosa dilecta in up to 10.6% yield, and the terpenoid part was specifically and equivalently labelled in the moieties derived from isopentenyl pyrophosphate and 3,3-dimethylallyl pyrophosphate. A similar labelling pattern, with incorporations of 0.06-0.1% was found for geraniol or nerol formed in leaves of Pelargonium graveolens The former results provide the best available evidence for the mevalonoid route to regular monoterpenes in higher plants. 2. Incorporation studies with 3RS-[2-(14)C,(4R)-4-(3)H(1)]-mevalonate and its (4S)-isomer showed that the pro-4R hydrogen atom of the precursor was retained and the pro-4S hydrogen atom was eliminated in both alcohols and both glucosides. These results suggest that the correlation of retention of the pro-4S hydrogen atom of mevalonate with formation of a cis-substituted double bond, such as has been found in certain higher terpenoids, does not apply to the biosynthesis of monoterpenes. It is proposed that either nerol is derived from isomerization of geraniol or the two alcohols are directly formed by different prenyltransferases. Possible mechanisms for these processes are discussed. 3. The experiments with [(14)C,(3)H]mevalonate also show that in these higher plants, as has been previously found in animal tissue and yeast, the pro-4S hydrogen atom of mevalonate was lost in the conversion of isopentenyl pyrophosphate into 3,3-dimethylallyl pyrophosphate.