Synthesis of 5,9-hexacosadienoic acid phospholipids. 11. Phospholipid studies of marine organisms

Mena, Philippe L.; Djerassi, Carl

doi:10.1016/0009-3084(85)90014-3

Cited by 25 publications

(8 citation statements)

References 32 publications

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“…1A. It is evident that a steady migration of the ⌬-bond from C(5) to C (8) and then to C(11) results in a progressive decrease in T m . However, the incremental drop in T m does not correspond proportionally to the stepwise increase in the ⌬ position.…”

Section: Resultsmentioning

confidence: 95%

Phosphatidylcholines with sn-−1 Saturated and sn-−2 cis-Monounsaturated Acyl Chains

Wang

Huo

et al. 1995

Journal of Biological Chemistry

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Recently, we have shown by high resolution differential scanning calorimetry that the position of a cis double bond (⌬-bond) in a series of 1-stearoyl-2-octadecenoyl-phosphatidylcholines can affect the phase transition temperature (T m ) or enthalpy (⌬H) of the gelto-liquid crystalline phase transition of this series of lipids in the following manner. The value of T m (or ⌬H) is minimal when the ⌬-bond is positioned at C(11) in the sn-2 acyl chain; in addition, this value increases steadily as the ⌬-bond migrates toward either end of the acyl chain, resulting in a symmetrical, inverted bell-shaped profile (Wang, Z.-q., Lin, H.-n., Li, S., and Huang, C. (1995) J. Biol. Chem. 270, 2014 -2023). In this communication, we have further demonstrated the inverted bell-shaped profile of T m using 1-arachidoyl-2-eicosenoyl-phosphatidylcholines. In addition, we have extended the lipid series of 1-stearoyl-2-octadecenoyl-phosphatidylcholines to include 1-arachidoyl-2-octadecenoyl-phosphatidylcholines and 1-behenoyl-2-octadecenoyl-phosphatidylcholine, each series with a ⌬-bond at varying carbon position of 6, 7, 9, 11, 12, and 13. Calorimetric results obtained with these three series of lipids indicate that the inverted bell-shaped curve shifts toward higher temperatures in a nonuniform manner as the saturated sn-1 acyl chain length increases from 17 to 19 and then to 21 C-C bond lengths. Specifically, the T m (or ⌬H) values are nearly identical for these cis-monoenoic lipids when their ⌬-bonds are positioned at C(13). Based on the height of the rotational energy barrier obtained with molecular mechanics calculations, it is evident that the rotational flexibility of the single C-C bond adjacent to the ⌬-bond in 1-stearoyl-2-octadecenoyl-phosphatidylcholine increases as the ⌬-bond migrates from C(9) to C(13). The differential scanning calorimetry results obtained with the three series of lipids can thus be attributed to an increase in the rotational flexibility of the short chain segment succeeding the C(14) atom in the sn-2 octadecenoyl chain. In this communication, we also propose that in the gel-state bilayer of sn-1 saturated/ sn-2 cis-monounsaturated phosphatidylcholine the entire length of the shorter segment of the sn-2 acyl chain acts as a structural perturbing element; hence, it is mainly responsible for the large lower T m of the monoenoic lipid relative to the saturated counterpart. Finally, two general equations relating T m with the structural parameters of cis-monoenoic phosphatidylcholines are presented. These equations, formulated primarily on the assumption that the short segment of the sn-2 acyl chain acts as a perturbing element, are shown to have strong predictive power in estimating the T m values of the gel-to-liquid crystalline phase transitions for sn-1 saturated/sn-2 cis-monounsaturated phosphatidylcholines.Phosphatidylcholines isolated from the plasma membrane of eukaryotic cells are a structurally diverse group of phospholipids. The bewildering variety of membrane phosphatidylcholines originates fro...

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Section: Resultsmentioning

confidence: 95%

Phosphatidylcholines with sn-−1 Saturated and sn-−2 cis-Monounsaturated Acyl Chains

Wang

Huo

et al. 1995

Journal of Biological Chemistry

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“…Three mixed-chain phosphatidylcholines, i.e., C(15):C(17)PC, C(17): C(15)PC, and C(12):C(20)PC, were semisynthesized at room temperature using a modified procedure of Mena and Djerassi (1985) as described required for the semisynthesis were purchased from Sigma (St. Louis, MO) and Avanti Polar Lipids (Alabaster, AL), respectively. The purity of the position isomers, C(15):C(17)PC and C(17):C(15)PC, was found to be extremely high (>99%), as judged from the DSC scans (see Results) and analytical thin-layer chromatography as reported previously (Li et al, 1996).…”

Section: Materials and Methods Phospholipidsmentioning

confidence: 99%

Probing the ethanol-induced chain interdigitations in gel-state bilayers of mixed-chain phosphatidylcholines

Huang¹,

McIntosh²

1997

Biophysical Journal

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Using high-resolution differential scanning calorimetry (DSC), we have studied the effects of ethanol concentrations, [EtOH], on the main phase transition temperatures (T[m]) of the following mixed-chain phosphatidylcholines (PCs): C(15):C(17)PC, C(17):C(15)PC, and C(12):C(20)PC. These lipids have a common molecular weight; however, their apparent acyl chain-length differences between the sn-1 and sn-2 acyl chains, delta C, are distinctively different. The delta C values for these three mixed-chain PCs are, respectively, 0.5, 3.5, and 6.5 C-C bond lengths. DSC results show that the T(m) profiles for C(15):C(17)PC and C(17):C(15)PC bilayers in the plot of T(m) versus [EtOH] are V-shaped biphasic curves, with the minimum T(m) occurring at 50 and 73 mg/ml of ethanol, respectively. In contrast, the C(12):C(20)PC bilayer exhibits a nearly linear decrease in T(m) with increasing [EtOH]. In addition, x-ray diffraction experiments were also performed to assess the structural changes of these three mixed-chain PCs in the gel-state bilayers, at 20 degrees C, in response to high concentrations of ethanol. X-ray diffraction data indicate that, in the absence of ethanol, these three lamellar lipids are all packed in the normal (L beta') gel phase in aqueous media. In the presence of 120 mg/ml of ethanol, however, the C(15):C(17)PC and C(17):C(15)PC lamellae are packed in the fully interdigitated (L beta[I]) gel phase. The V-shaped T(m) curves detected calorimetrically for these two lipids in response to [EtOH] can thus be explained by the ethanol-induced L beta' --> L beta[I] isothermal phase transition. Interestingly, the results of x-ray diffraction study reveal, for the first time, that an ethanol-induced L beta' --> L(MI) (mixed interdigitated phase) isothermal phase transition occurs in the gel-state bilayer of highly asymmetrical C(12):C(20)PC. Therefore, the chain asymmetry is recognized to play an important role in the ethanol-induced chain interdigitation at T < T(m).

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“…A series of mixed-chain PCs was prepared semisynthetically at room temperature using the modified procedure of Mena and Djerassi (1985) as described previously (Lin et al, 1990). This series of mixed-chain PC contains the following five molecular species: C(15):C(17)PC, C(14): C(18)PC, C(17):C(l5)PC, C(13):C(l9)PC, and C(12):C(20)PC, each of which has the same total number of chain methylene units as that of DPPC.…”

Section: Semisynthesis Of Saturated Mixed-chain Phosphatidylcholinesmentioning

confidence: 99%

Effects of alcohols on the phase transition temperatures of mixed-chain phosphatidylcholines

Li¹,

Huo²,

Wang³

et al. 1996

Biophysical Journal

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The biphasic effect of ethanol on the main phase transition temperature (Tm) of identical-chain phosphatidyl-cholines (PCs) in excess H2O is now well known. This biphasic effect can be attributed to the transformation of the lipid bilayer, induced by high concentrations of ethanol, from the partially interdigitated L beta, phase to the fully interdigitated L beta I phase at T < Tm. The basic packing unit of the L beta I phase has been identified recently as a binary mixture of PC/ethanol at the molar ratio of 1:2. The ethanol effect on mixed-chain PCs, however, is not known. We have thus in this study investigated the alcohol effects on the Tm of mixed-chain PCs with different delta C values, where delta C is the effective acyl chain length difference between the sn-1 and sn-2 acyl chains. Initially, molecular mechanics (MM) simulations are employed to calculate the steric energies associated with a homologous series of mixed-chain PCs packed in the partially and the fully interdigitated L beta I motifs. Based on the energetics, the preference of each mixed-chain PC for packing between these two different motifs can be estimated. Guided by MM results, high-resolution differential scanning calorimetry is subsequently employed to determine the Tm values for aqueous lipid dispersions prepared individually from a series of mixed-chain PCs (delta C = 0.5-6.5 C-C bond lengths) in the presence of various concentrations of ethanol. Results indicate that aqueous dispersions prepared from mixed-chain PCs with a delta C value of less than 4 exhibit a biphasic profile in the plot of Tm versus ethanol concentration. In contrast, highly asymmetric PCs (delta C > 4) do not exhibit such biphasic behavior. In the presence of a longer chain n-alcohol, however, aqueous dispersions of highly asymmetric C(12):C(20)PC (delta C = 6.5) do show such biphasic behavior against ethanol. Our results suggest that the delta C region in a highly asymmetric PC packed in the L beta I phase is most likely the binding site for n-alcohol.

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Synthesis of 5,9-hexacosadienoic acid phospholipids. 11. Phospholipid studies of marine organisms

Cited by 25 publications

References 32 publications

Phosphatidylcholines with sn-−1 Saturated and sn-−2 cis-Monounsaturated Acyl Chains

Phosphatidylcholines with sn-−1 Saturated and sn-−2 cis-Monounsaturated Acyl Chains

Probing the ethanol-induced chain interdigitations in gel-state bilayers of mixed-chain phosphatidylcholines

Effects of alcohols on the phase transition temperatures of mixed-chain phosphatidylcholines

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