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D de Boer

Publications and source records attributed to D de Boer.

23 records · Page 2Linked to original sources
PubMed1988

In vivo import of plastocyanin and a fusion protein into developmentally different plastids of transgenic plants.

Transgenic tomato plants that constitutively express a foreign plastocyanin gene were used to study protein transport in different tissues. Normally expression of endogenous plastocyanin genes in plants is restricted to photosynthetic tissues only, whereas this foreign plastocyanin protein is found to be present in all tissues examined. The protein is transported into the local plastids in these tissues and it is processed to the mature size. We conclude that plastids of developmentally different tissues are capable of importing precursor proteins that are normally not found in these tissues. Most likely such plastids, though functionally and morphologically differentiated, have similar or identical protein import mechanisms when compared to the chloroplasts in green tissue.

Chloroplasts↗
PubMed1986

The peplomers of Berne virus.

Using [3H]glucosamine and [3H]mannose labels, two virus-specific glycosylated polypeptide species with Mr values of about 200,000 (200K) and in the 75K to 100K range, respectively, were recognized in Berne virus-infected embryonic mule skin cells. In purified virions only the latter glycoprotein occurred. Concanavalin A was bound to the virion as evidenced by reduction in infectivity. Analyses using SDS-PAGE, blotting and glycoprotein identification with concanavalin A and horseradish peroxidase showed coincidence of the virion glycoprotein signals with the maximum infectivity and haemagglutinating activity in an isokinetic sucrose gradient. Polyclonal rabbit immune serum and a neutralizing and haemagglutination-inhibiting monoclonal antibody raised against Berne virus recognized both the 75K to 100K and the '200K' glycoproteins. Using tunicamycin, a concentration-dependent inhibition of infectivity was noted; however, non-infectious particles containing the two major polypeptides (20K and 22K) were released from the cells in small quantities. The glycoproteins were absent from cytoplasmic extracts and a novel polypeptide of about 150K was identified instead. Translation of poly(A)-selected intracellular RNA from infected cells in a rabbit reticulocyte cell-free system also resulted in the appearance of a new high Mr polypeptide (about 170K). Using pulse-chase labelling and radioimmunoprecipitation, suggestive evidence for a precursor-product relationship between the intracellular '200K' and the virion glycoproteins has been obtained. These experiments identify the N-glycosylated proteins in the 75K to 100K range as constituents of the peplomeric envelope projection of Berne virus; they probably arise by post-translational processing of a 150K to 170K precursor molecule involving glycosylation and subsequent cleavage.

Antibodies, Viral↗
PubMedDate not supplied

The detection of danazol and its significance in doping analysis.

The use of anabolic steroids and related compounds in sport is forbidden by the International Olympic Committee (IOC). Because danazol (17 alpha-pregna-2,4-dien-20-yno[2,3-D] isoxazol-17 beta-ol) is structurally related to the anabolic steroid stanozolol, its use should be questioned. Therefore, the detection and the significance of danazol in doping analysis are discussed. A urine specimen suspected of containing danazol metabolites was analyzed in order to characterize the metabolites. After isolation and conversion into three different derivatives, the metabolites were subjected to gas chromatography/mass spectrometry (GC/MS) in the electron impact (EI) mode. The structure assignment was based on the molecular ions, fragmentation patterns observed for the three different derivatives, and the possible metabolite structures given in the literature. Ethisterone was identified as a nonconjugated metabolite. 2-Hydroxymethylethisterone was observed in two stereoisomeric forms. One stereoisomer was found mainly in the nonconjugated steroid fraction and the other in the conjugated fraction. The results were confirmed by analyzing urine specimens of a volunteer who was known to have taken danazol. Derivatization methods and GC/MS data are given to implement danazol detection in routine screening and confirmation procedures.

Danazol↗