A Linear Epitope in the N-Terminal Domain of CCR5 and Its Interaction with Antibody.

The CCR5 receptor plays a role in several key physiological and pathological processes and is an important therapeutic target. Inhibition of the CCR5 axis by passive or active immunisation offers one very selective strategy for intervention. In this study we define a new linear epitope within the extracellular domain of CCR5 recognised by two independently produced monoclonal antibodies. A short peptide encoding the linear epitope can induce antibodies which recognise the intact receptor when administered colinear with a tetanus toxoid helper T cell epitope. The monoclonal antibody RoAb 13 is shown to bind to both cells and peptide with moderate to high affinity (6x10^8 and 1.2x107 M-1 respectively), and binding to the peptide is enhanced by sulfation of tyrosines at positions 10 and 14. RoAb13, which has previously been shown to block HIV infection, also blocks migration of monocytes in response to CCR5 binding chemokines and to inflammatory macrophage conditioned medium. A Fab fragment of RoAb13 has been crystallised and a structure of the antibody is reported to 2.1 angstrom resolution

Stability of belladonna mottle virus particles: the role of polyamines and calcium

The stability of belladonna mottle virus (BDMV) has been studied with respect to elevated pH and to freezing and thawing. BDMV, purified by a modified procedure, was stable at alkaline pH, in contradiction to earlier reports. This difference in the stability could be attributed to the presence of 90 to 140 molecules of spermidine, 20 to 50 molecules of putrescine and 500 to 900 calcium ions in each virus particle. The polyamines could be easily exchanged with other cations such as potassium or caesium and this resulted in a loss of particle stability. These cations may therefore play a role in maintaining the integrity of particle structure. The formation of empty protein shells as a result of freezing and thawing BDMV particles parallels earlier observations on turnip yellow mosaic virus particles

A formal total synthesis of (±)-homogynolide-B

A formal total synthesis of (±)-homogynolide-B, a sesquiterpene containing an α-spiro-β-methylene-γ-butyrolactone moiety spirofused to a bicyclo[4.3.0]nonane framework, is described. Thus, Hagemann's ester 11 was converted into the allyl alcohol 16 in three steps. One-pot Claisen rearrangement of the allyl alcohol 16 and 2-methoxypropene in the presence of a catalytic amount of propionic acid afforded a 3:2 epimeric mixture of the ketone 15 and further rearranged product 19. Ozonolysis followed by intramolecular aldol condensation and hydrogenation transformed the enones 15a,b into the key intermediate keto ketals 13a and 13b. Methoxymethylene Wittig reaction followed by bromoacetalisation converted the keto ketal 13a into the radical precursor bromo acetal 22a. The 5-exo-dig radical cyclisation of the bromo acetal 22a, followed by acid catalysed hydrolysis and oxidation, led to the keto spirolactone 12, Greene's precursor of homogynolide-B. The same sequence transformed the keto ketal 13b into a 3:2 mixture of the spirolactones 12 and 25, which on equilibration furnished the spirolactone 12. The stereostructure of the keto spirolactone 12 was unambiguously established by single-crystal X-ray diffraction analysis

A formal total synthesis of (±)-homogynolide-B

A formal total synthesis of (+/-)-homogynolide-B, a sesquiterpene containing an alpha-spiro-beta-methylene-gamma-butyrolactone moiety spirofused to a bicyclo[4.3.0]nonane framework, is described. Thus, Hagemann's ester 11 was converted into the allyl alcohol 16 in three steps. One-pot Claisen rearrangement of the allyl alcohol 16 and 2-methoxypropene in the presence of a catalytic amount of propionic acid afforded a 3:2 epimeric mixture of the ketone 15 and further rearranged product 19. Ozonolysis followed by intramolecular aldol condensation and hydrogenation transformed the enones 15a,b into the key intermediate keto ketals 13a and 13b. Methoxymethylene Wittig reaction followed by bromoacetalisation converted the keto ketal 13a into the radical precursor bromo acetal 22a. The 5-exo-dig radical cyclisation of the bromo acetal 22a, followed by acid catalysed hydrolysis and oxidation, led to the keto spirolactone 12, Greene's precursor of homogynolide-B. The same sequence transformed the keto ketal 13b into a 3:2 mixture of the spirolactones 12 and 25, which on equilibration furnished the spirolactone 12. The stereostructure of the keto spirolactone 12 was unambiguously established by single-crystal X-ray diffraction analysis