Biomedical subjects

R Caubergs

Publications and source records attributed to R Caubergs.

At least 19 recordsLinked to original sources

PubMed2006

Accumulation of tocopherols and tocotrienols during seed development of grape (Vitis vinifera L. cv. Albert Lavallée).

Tocopherols and tocotrienols are present in mature seeds. Yet, little is known about the physiological role and the metabolism of these compounds during seed development. Here we present data on tocopherol and tocotrienol accumulation during seed development in Vitis vinifera L. cv. Albert Lavallée (Royal). This species was chosen for its ability to synthesize both tocopherols and tocotrienols. It is shown here for the first time that during seed development there are significant differences in localization and accumulation kinetics of tocopherols and tocotrienols. Tocopherols are found homogeneously dispersed throughout all tissues of the seed, in concentrations ranging from 20 to 100 microg tocopherol per g dry weight. Tocopherol levels decrease gradually during seed development. In contrast, tocotrienols are only found in the endosperm of the seeds, accumulating in a sigmoid fashion during the maturation period of seed development. Tocotrienol levels were found to be (54+/-7.4) microg/g dry seed in 90-day-old seeds of V. vinifera L. Furthermore, tocotrienol biosynthesis is demonstrated in these seeds during tocotrienol accumulation and in an endosperm fraction isolated at 75 days after flowering.

Seeds↗

PubMed2001

Biochemical characterization and ligand binding properties of neuroglobin, a novel member of the globin family.

Neuroglobin is a recently discovered member of the globin superfamily that is suggested to enhance the O(2) supply of the vertebrate brain. Spectral measurements with human and mouse recombinant neuroglobin provide evidence for a hexacoordinated deoxy ferrous (Fe(2+)) form, indicating a His-Fe(2+)-His binding scheme. O(2) or CO can displace the endogenous protein ligand, which is identified as the distal histidine by mutagenesis. The ferric (Fe(3+)) form of neuroglobin is also hexacoordinated with the protein ligand E7-His and does not exhibit pH dependence. Flash photolysis studies show a high recombination rate (k(on)) and a slow dissociation rate (k(off)) for both O(2) and CO, indicating a high intrinsic affinity for these ligands. However, because the rate-limiting step in ligand combination with the deoxy hexacoordinated form involves the dissociation of the protein ligand, O(2) and CO binding is suggested to be slow in vivo. Because of this competition, the observed O(2) affinity of recombinant human neuroglobin is average (1 torr at 37 degrees C). Neuroglobin has a high autoxidation rate, resulting in an oxidation at 37 degrees C by air within a few minutes. The oxidation/reduction potential of mouse neuroglobin (E'(o) = -129 mV) lies within the physiological range. Under natural conditions, recombinant mouse neuroglobin occurs as a monomer with disulfide-dependent formation of dimers. The biochemical and kinetic characteristics are discussed in view of the possible functions of neuroglobin in the vertebrate brain.

Animals↗

PubMed1989

b-Type Cytochromes in Higher Plant Plasma Membranes.

The composition and characteristics of b-type cytochromes from higher plant plasma membranes, purified using aqueous two-phase partitioning, were investigated. At least three different cytochromes were identified by their wavelength maxima and redox midpoint potentials (E(0)'). Cytochrome b-560.7 (E(0)' from + 110 to + 160 millivolts) was present in zucchini (Cucurbita pepo) hypocotyls and bean (Phaseolus vulgaris L.) hooks, although in different concentrations. The main component in cauliflower (Brassica oleracea L.) inflorescences (cytochrome b-558.8) is probably functionally similar to this cytochrome. The plasma membrane generally contains two to three cytochrome species. However, the occurrence and concentrations were species dependent. The high potential cytochrome can be reduced by ascorbate but not NADH, and may be involved in blue light perception.

Journal Article↗

PubMed1979