β-Carotene as a probe of lipid domains of reconstituted human plasma Low-Density Lipoprotein

Induced Circular Dichroism

G. Chi Chen, Monty Krieger, John P. Kane, Chuen Shang C Wu, Michael S. Brown, Joseph L. Goldstein

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Mixtures of neutral lipids containing cholesteryl esters and β-carotene were used to reconstitute the lipid core of heptane-extracted low-density lipoproteins (LDL). The resulting preparations of reconstituted LDL, referred to as r-[cholesteryl ester + β-carotene]LDL, exhibited temperature-dependent circular dichroism (CD) in the visible region similar to that of native LDL. Since β-carotene lacks intrinsic optical asymmetry, the observed CD must be induced by environmental constraint. LDL reconstituted with cholesteryl oleate, cholesteryl linoleate, or cholesteryl linolenate in the presence of β-carotene exhibited thermotropic transitions at approximately 40, 35, and 30°C, respectively. These temperatures are similar to the liquid-crystalline to isotropic liquid phase transition temperatures observed for pure cholesteryl ester model systems. The addition of triolein to r-[cholesteryl linoleate + β-carotene]LDL lowered the transition temperature and decreased the specific ellipticity of the visible CD bands. When triolein accounted for 70% or more of the total neutral lipid content of r-[cholesteryl linoleate + triolein + β-carotene]LDL, specific ellipticity was zero. The addition of low levels of unesterified cholesterol to r-[cholesteryl linoleate + β-carotene]LDL did not alter the transition temperature but did reduce the specific ellipticity by 40%. The current data indicate that the organization of the core of neutral lipids in reconstituted LDL resembles that of native LDL with respect to environmental constraint on the β-carotene molecule and that the helicity of the protein moiety resembles that of native LDL. In addition, the data are consistent with the possibility that the core cholesteryl esters of reconstituted LDL undergo phase transitions similar to their transitions in the free state.

Original languageEnglish (US)
Pages (from-to)4706-4712
Number of pages7
JournalBiochemistry
Volume19
Issue number20
StatePublished - 1980

Fingerprint

Plasma (human)
Carotenoids
Circular Dichroism
LDL Lipoproteins
Lipids
Cholesterol Esters
Triolein
Transition Temperature
Phase Transition
Phase transitions
Heptanes
Temperature
Liquids

ASJC Scopus subject areas

  • Biochemistry

Cite this

β-Carotene as a probe of lipid domains of reconstituted human plasma Low-Density Lipoprotein : Induced Circular Dichroism. / Chen, G. Chi; Krieger, Monty; Kane, John P.; Wu, Chuen Shang C; Brown, Michael S.; Goldstein, Joseph L.

In: Biochemistry, Vol. 19, No. 20, 1980, p. 4706-4712.

Research output: Contribution to journalArticle

@article{89dde36fc8834514be1d20a9bba50f15,
title = "β-Carotene as a probe of lipid domains of reconstituted human plasma Low-Density Lipoprotein: Induced Circular Dichroism",
abstract = "Mixtures of neutral lipids containing cholesteryl esters and β-carotene were used to reconstitute the lipid core of heptane-extracted low-density lipoproteins (LDL). The resulting preparations of reconstituted LDL, referred to as r-[cholesteryl ester + β-carotene]LDL, exhibited temperature-dependent circular dichroism (CD) in the visible region similar to that of native LDL. Since β-carotene lacks intrinsic optical asymmetry, the observed CD must be induced by environmental constraint. LDL reconstituted with cholesteryl oleate, cholesteryl linoleate, or cholesteryl linolenate in the presence of β-carotene exhibited thermotropic transitions at approximately 40, 35, and 30°C, respectively. These temperatures are similar to the liquid-crystalline to isotropic liquid phase transition temperatures observed for pure cholesteryl ester model systems. The addition of triolein to r-[cholesteryl linoleate + β-carotene]LDL lowered the transition temperature and decreased the specific ellipticity of the visible CD bands. When triolein accounted for 70{\%} or more of the total neutral lipid content of r-[cholesteryl linoleate + triolein + β-carotene]LDL, specific ellipticity was zero. The addition of low levels of unesterified cholesterol to r-[cholesteryl linoleate + β-carotene]LDL did not alter the transition temperature but did reduce the specific ellipticity by 40{\%}. The current data indicate that the organization of the core of neutral lipids in reconstituted LDL resembles that of native LDL with respect to environmental constraint on the β-carotene molecule and that the helicity of the protein moiety resembles that of native LDL. In addition, the data are consistent with the possibility that the core cholesteryl esters of reconstituted LDL undergo phase transitions similar to their transitions in the free state.",
author = "Chen, {G. Chi} and Monty Krieger and Kane, {John P.} and Wu, {Chuen Shang C} and Brown, {Michael S.} and Goldstein, {Joseph L.}",
year = "1980",
language = "English (US)",
volume = "19",
pages = "4706--4712",
journal = "Biochemistry",
issn = "0006-2960",
publisher = "American Chemical Society",
number = "20",

}

TY - JOUR

T1 - β-Carotene as a probe of lipid domains of reconstituted human plasma Low-Density Lipoprotein

T2 - Induced Circular Dichroism

AU - Chen, G. Chi

AU - Krieger, Monty

AU - Kane, John P.

AU - Wu, Chuen Shang C

AU - Brown, Michael S.

AU - Goldstein, Joseph L.

PY - 1980

Y1 - 1980

N2 - Mixtures of neutral lipids containing cholesteryl esters and β-carotene were used to reconstitute the lipid core of heptane-extracted low-density lipoproteins (LDL). The resulting preparations of reconstituted LDL, referred to as r-[cholesteryl ester + β-carotene]LDL, exhibited temperature-dependent circular dichroism (CD) in the visible region similar to that of native LDL. Since β-carotene lacks intrinsic optical asymmetry, the observed CD must be induced by environmental constraint. LDL reconstituted with cholesteryl oleate, cholesteryl linoleate, or cholesteryl linolenate in the presence of β-carotene exhibited thermotropic transitions at approximately 40, 35, and 30°C, respectively. These temperatures are similar to the liquid-crystalline to isotropic liquid phase transition temperatures observed for pure cholesteryl ester model systems. The addition of triolein to r-[cholesteryl linoleate + β-carotene]LDL lowered the transition temperature and decreased the specific ellipticity of the visible CD bands. When triolein accounted for 70% or more of the total neutral lipid content of r-[cholesteryl linoleate + triolein + β-carotene]LDL, specific ellipticity was zero. The addition of low levels of unesterified cholesterol to r-[cholesteryl linoleate + β-carotene]LDL did not alter the transition temperature but did reduce the specific ellipticity by 40%. The current data indicate that the organization of the core of neutral lipids in reconstituted LDL resembles that of native LDL with respect to environmental constraint on the β-carotene molecule and that the helicity of the protein moiety resembles that of native LDL. In addition, the data are consistent with the possibility that the core cholesteryl esters of reconstituted LDL undergo phase transitions similar to their transitions in the free state.

AB - Mixtures of neutral lipids containing cholesteryl esters and β-carotene were used to reconstitute the lipid core of heptane-extracted low-density lipoproteins (LDL). The resulting preparations of reconstituted LDL, referred to as r-[cholesteryl ester + β-carotene]LDL, exhibited temperature-dependent circular dichroism (CD) in the visible region similar to that of native LDL. Since β-carotene lacks intrinsic optical asymmetry, the observed CD must be induced by environmental constraint. LDL reconstituted with cholesteryl oleate, cholesteryl linoleate, or cholesteryl linolenate in the presence of β-carotene exhibited thermotropic transitions at approximately 40, 35, and 30°C, respectively. These temperatures are similar to the liquid-crystalline to isotropic liquid phase transition temperatures observed for pure cholesteryl ester model systems. The addition of triolein to r-[cholesteryl linoleate + β-carotene]LDL lowered the transition temperature and decreased the specific ellipticity of the visible CD bands. When triolein accounted for 70% or more of the total neutral lipid content of r-[cholesteryl linoleate + triolein + β-carotene]LDL, specific ellipticity was zero. The addition of low levels of unesterified cholesterol to r-[cholesteryl linoleate + β-carotene]LDL did not alter the transition temperature but did reduce the specific ellipticity by 40%. The current data indicate that the organization of the core of neutral lipids in reconstituted LDL resembles that of native LDL with respect to environmental constraint on the β-carotene molecule and that the helicity of the protein moiety resembles that of native LDL. In addition, the data are consistent with the possibility that the core cholesteryl esters of reconstituted LDL undergo phase transitions similar to their transitions in the free state.

UR - http://www.scopus.com/inward/record.url?scp=0019175656&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0019175656&partnerID=8YFLogxK

M3 - Article

VL - 19

SP - 4706

EP - 4712

JO - Biochemistry

JF - Biochemistry

SN - 0006-2960

IS - 20

ER -