Physical studies of myelin I. Thermal analysis

Ladbrooke, B.D.; Jenkinson, T.J.; Kamat, V.B.; Chapman, D.

doi:10.1016/0005-2760(68)90076-3

Cited by 101 publications

(22 citation statements)

References 24 publications

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“…In fact, our lipid analyses (see Results) show the virtual disappearance of cholesterol and plasmalogens as well as a lower proportion of free fatty acids, phosphatidylcholine and esphingomyelin in crude PLP compared to the lipid composition of white matter and of myelin. A similar conclusion had already been arrived at by Ladbrooke et al (1968), who observed no thermal transition in lipids extracted from myelin; after eliminating cholesterol from their lipids, however, a thermal transition was found at 50 °C with an enthalpy of 12 J/g. These values compare well with ours for the lipids extracted from crude PLP (Table 1).…”

Section: Discussionsupporting

confidence: 83%

The thermal transition in crude myelin proteolipid has a lipid rather than protein origin

et al. 1992

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Myelin proteolipid has been isolated from bovine brain and purified using organic solvents according to conventional procedures. The protein content of the purified sample, or crude proteolipid, contains a minimum of 75% w/w of proteolipid, with DM-20, a proteolipid molecule with an internal deletion of 35 out of 276 amino acid residues, as the only other component. Biochemical analysis has shown the differences in lipid composition between brain white matter, myelin and crude proteolipid preparations. The latter contained practically no cholesterol, while the other two samples had about 22-23% w/w. High-sensitivity differential scanning calorimetry experiments with both crude proteolipid and its extracted pool of lipids have shown similar reversible thermal transitions at 52 degrees C and 48 degrees C. The effect of increasing amounts of cholesterol on the two calorimetric transitions led in both cases to a continuous decrease in the melting temperature and in the transition enthalpy. Parallel Fourier-transform infrared spectroscopy studies of crude proteolipid have detected a reversible, co-operative lipid transition centred at 49 degrees C, with no detectable change in the amide region between 20 degrees C and 60 degrees C. Once more an increase in cholesterol content led to a decrease in the sharpness of this transition. It is concluded that the thermal transition detected in crude proteolipid, which has in the past been attributed to proteolipid thermal denaturation (Mateo et al. 1986), actually corresponds to a thermotropic phase transition of the lipids included in the crude proteolipid sample.

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Section: Discussionsupporting

confidence: 83%

The thermal transition in crude myelin proteolipid has a lipid rather than protein origin

et al. 1992

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“…Investigation into the thermal behaviour of myelin membrane have generally been directed towards the phase transitions of the lipids or lipid fractions present in the membrane (Ladbrooke et al 1968;Johnston and Chapman 1988), as is usual with the majority of biomcmbranes (Sfinchez-Ruiz and Mateo 1987). Our high-sensitivity DSC results, complemented by those of FTIR and, particularly, TGA, have allowed us to characterize the thermal stability of myelin proteins, except for MBP.…”

Section: Discussionmentioning

confidence: 99%

“…Our high-sensitivity DSC results, complemented by those of FTIR and, particularly, TGA, have allowed us to characterize the thermal stability of myelin proteins, except for MBP. A few papers have been published on DSC studies into myelin, for example that by Moscarello et al (1983) with human CNS myelin, where no enthalpy data were reported, and those of Chapman and co-workers (Ladbrooke et al 1968;Johnston and Chapman 1988) with myelin from ox brain and from guinea pig CNS, where no transition was assigned to the myelin proteins. The general features of our DSC results for native myelin (Fig.…”

Section: Discussionmentioning

confidence: 99%

Thermal stability of bovine-brain myelin membrane

et al. 1992

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The thermal behaviour of bovine-brain myelin membrane has been studied by high-sensitivity differential scanning calorimetry, Fourier-transform infrared spectroscopy and thermal gel analysis. Spectroscopic results indicate that protein transitions take place between 60 degrees C and 90 degrees C, while thermal gel analysis has provided the thermal denaturation profiles of myelin proteolipid, DM-20 protein and the Wolfgram Fraction. An irreversible calorimetric transition centred at 80.3 +/- 0.2 degrees C with a specific enthalpy of 4.7 +/- 0.6 J/g of total protein has been assigned to the thermal denaturation of myelin proteolipid and DM-20 protein. The effects of the myelin storage conditions, scan rate, ionic strength and pH on this calorimetric transition have also been investigated. The thermal transition of the proteolipid practically disappears after treatment of the myelin with different amounts of chloroform-methanol 2:1 (v/v), a treatment which is generally used in proteolipid purification. On the other hand, the addition of several detergents to myelin only causes minor modifications to this transition, which then occurs at about 70 degrees C, with a specific enthalpy of between 2.5 and 3.6 J/g of total protein. These results appear to show that detergents preserve the native conformation of the proteolipid far more than do organic solvents. Hence the use of detergents would seem to be the appropriate method for proteolipid purification.

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“…The presence of long chain fatty acids in cerebrosides gives the lipid a high phase transition temperature which is around 70 0 C for cerebrosides in the hydrated state (7). The position of the transition can be reduced by interaction of cerebroside with cholesterol (10) or with phospholipids such as phosphatidyl choline (3).…”

Section: Introductionmentioning

confidence: 99%

On the Accessibility and Localisation of Cerebrosides in Central Nervous System Myelin

Linington

Rumsby

1978

Advances in Experimental Medicine and Biology

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SUMMARYCerebrosides are concentrated in the myelin sheath where they account for about 20% of the total lipid of the membrane. The present paper is concerned with the role and localisation of these glycolipids in the myelin lamellae. Isolated central nerve myelin preparations have been treated with two probes to investigate cerebroside accessibility in the membrane. The action of galactose oxidase on the galactose headgroups of cerebrosides is followed and quanti tated by recovery of the modified glycolipid and resoluGion of either the 6-aldehydo sugar or galactose remaining by gasliquid chromatography. With isolated myelin preparations only some 40-50% of the cerebroside galactose is attacked by galactose oxidase at 20 0 C. With periodate at 20 0 C over 90% of the galactose headgroups are oxidised in 3 h while the figure is 50-55% over the same time period at 4°c rising to 85% after 22 h. With multilamellar liposomes of mixed myelin ligids only some 20-25% of the available cerebroside is oxidised at 4 C, the reaction being complete in 2 h. The results are discussed in relation to the disposition of cerebroside in the myelin lamellae. A major location on the external face of the membrane system (intraperiod dense line) is favoured. A role for cerebroside in myelin in terms of increasing the stability and resistance of the lipid phase to ion movement is suggested.

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Physical studies of myelin I. Thermal analysis

Cited by 101 publications

References 24 publications

The thermal transition in crude myelin proteolipid has a lipid rather than protein origin

The thermal transition in crude myelin proteolipid has a lipid rather than protein origin

Thermal stability of bovine-brain myelin membrane

On the Accessibility and Localisation of Cerebrosides in Central Nervous System Myelin

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