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H A Blair

Publications and source records attributed to H A Blair.

17 recordsLinked to original sources
PubMed1979

The importance of the phospholipid bilayer and the length of the cholesterol molecule in membrane structure.

The properties of mixtures of phosphatidylcholine and analogues of cholesterol bearing side chains of varying lengths were examined by a variety of methods. The incorporation of the analogues into sonicated liposomes and their effect on the rate of osmotic shrinking of multilamellar liposomes were determined. The ordering of a steroid spin label was studied in an oriented multibilayer system and the effect of the analogues on the phase transition of dipalmitoyl phosphatidylcholine monitored using the spin label TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl). Mixtures of analogues and phospholipid were also studied in monolayers. In all the bilayer systems studied cholesterol caused the greatest 'rigidifying' effect, the analogues with shorter or longer side chains being less effective. However, in the monolayer experiments the length of the sterol molecule was found to be much less critical. It is suggested that cholesterol is anchored in position in a phospholipid bilayer by virtue of the molecule being the precise length required to maximise interactions between neighbouring molecules without disturbing the bilayer structure.

Cholesterol↗
PubMed1976

Oxidation of cholesterol and cholesterol analogues by mitochondrial preparations of steroid-hormone-producing tissue.

The rate of oxidation of cholesterol and its analogues to pregnenolone (3beta-hydroxypregn-5-en-20-one) by various mitochondrial preparations was measured. Sterols with the cholest-5-en-3beta-ol ring system and saturated side chains of different lengths were converted into pregnenolone rat rates similar to that of cholesterol. This marked lack of mitochondrial specificity towards the steroid side chains is in direct contrast with the rat liver microsomal cholesterol 7alpha-hydroxylase, which has a high specificity for the side chain. Steroids that retain the ring system, but contain hydroxyl groups at various points in the side chain, are converted into pregnenolone at rates three to eight times higher than in cholesterol. The results are discussed with reference to current ideas on the mechanism of the side-chain cleavage of cholesterol. The results are discussed with reference to current ideas on the mechanism of the side-chain cleavage of cholesterol.

Adrenal Cortex↗
PubMed1968

Determination of oestrogen monoglucuronides by the Brown method.

In the Brown (Brown, 1955; Brown, Bulbrook & Greenwood, 1957) procedure for the determination of urinary oestrogens, losses may occur during the hydrolysis of the oestrogen conjugates and during the purification of the oestrogens thus formed. Losses during the latter stages were measured previously by adding free oestrogens to the hydrolysed urine. In the present study losses during acid and enzyme hydrolysis were measured by adding synthetic oestrogen monoglucuronides to urine.

Journal Article↗