Effect of Alkyl Chain Length on Molecular Heat Transfer Characteristics in Lipid Bilayers

2011 ◽  
Author(s):  
Takeo Nakano ◽  
Gota Kikugawa ◽  
Taku Ohara
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Lipid Bilayers ◽  
Chain Length ◽  
Phosphatidyl Choline ◽  
Acyl Chain ◽  
Nonequilibrium Molecular Dynamics ◽  
Acyl Chain Length ◽  
Acyl Chains ◽  
Dynamics Simulations

Nonequilibrium molecular dynamics simulations are carried out on single component lipid bilayers with ambient water in order to investigate the effect of acyl chain length on heat transport characteristics along and across the membranes. In this study, dipalmitoyl-phosphatidyl-choline (DPPC), dilauroyl-phosphatidyl-choline (DLPC), and stearoyl-myristoyl-phosphatidyl-choline (SMPC) which has two acyl chains of both sixteen C atoms, both twelve C atoms, and eighteen and fourteen C atoms, respectively, were used as lipid molecules. In the direction along the membranes, thermal conductivity corresponds with that of each membrane. On the other hand, in the direction across membrane, the highest thermal resistance exists at the center of lipid bilayer where lipid acyl chains face each other. However, asymmetric chain length reduces thermal resistance at the interface between lipid monolayers. Therefore, thermal conductivity across the membrane which consists of asymmetric chain length is higher than those which consist of symmetric chain length.

Effect of acyl chain length on the structure and motion of gramicidin A in lipid bilayers

1989 ◽  
Vol 985 (2) ◽  
pp. 229-232 ◽  
Author(s):  
Bruce A. Cornell ◽  
Frances Separovic ◽  
Denise E. Thomas ◽  
Annette R. Atkins ◽  
Ross Smith
Keyword(s):  
Lipid Bilayers ◽  
Chain Length ◽  
Acyl Chain ◽  
Gramicidin A ◽  
Structure And Motion ◽  
Acyl Chain Length

scholarly journals The elongation of exogenous fatty acids and the control of phospholipid acyl chain length in Micrococcus cryophilus

1980 ◽  
Vol 188 (3) ◽  
pp. 585-592 ◽  
Author(s):  
S P Sandercock ◽  
N J Russell
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Chain Length ◽  
De Novo ◽  
Acyl Chain ◽  
Psychrophilic Bacterium ◽  
Fatty Acid Elongation ◽  
Acyl Chain Length ◽  
Acyl Chains ◽  
Phospholipid Acyl Chain

The synthesis of fatty acids de novo from acetate and the elongation of exogenous satuated fatty acids (C12-C18) by the psychrophilic bacterium Micrococcus cryophilus (A.T.C.C. 15174) grown at 1 or 20 degrees C was investigated. M. cryophilus normally contains only C16 and C18 acyl chains in its phospholipids, and the C18/C16 ratio is altered by changes in growth temperature. The bacterium was shown to regulate strictly its phospholipid acyl chain length and to be capable of directly elongating myristate and palmitate, and possibly laurate, to a mixture of C16 and C18 acyl chains. Retroconversion of stearate into palmitate also occurred. Fatty acid elongation could be distinguished from fatty acid synthesis de novo by the greater sensitivity of fatty acid elongation to inhibition by NaAsO2 under conditions when the supply of ATP and reduced nicotinamide nucleotides was not limiting. It is suggested that phospholipid acyl chain length may be controlled by a membrane-bound elongase enzyme, which interconverts C16 and C18 fatty acids via a C14 intermediate; the activity of the enzyme could be regulated by membrane lipid fluidity.

scholarly journals Phospholipase activity on N-acyl phosphatidylethanolamines is critically dependent on the N-acyl chain length

2003 ◽  
Vol 374 (1) ◽  
pp. 109-115 ◽  
Author(s):  
Julio J. CARAMELO ◽  
Jorge FLORIN-CHRISTENSEN ◽  
José M. DELFINO
Keyword(s):  
Phospholipase A2 ◽  
Chain Length ◽  
Acyl Chain ◽  
Conformational Space ◽  
Head Group ◽  
Polar Head Group ◽  
Conformational Variability ◽  
Acyl Chain Length ◽  
Dynamics Simulations ◽  
Phospholipase A2 Activity

We have recently shown that an endogenous phospholipase A2 from bovine erythrocytes does not hydrolyse NAPEs (N-acyl l-α-phosphatidylethanolamines), which accumulate remarkably in this system [Florin-Christensen, Suarez, Florin-Christensen, Wainszelbaum, Brown, McElwain and Palmer (2001) Proc. Natl. Acad. Sci. U.S.A. 98, 7736–7741]. Here we investigate the causes underlying this resistance. N-acylation of PE (l-α-phosphatidylethanolamine) results in alteration of charge, head-group volume and conformation, the last two features depending on the N-acyl chain length. To evaluate each effect separately, we synthesized NAPEs with selected N-acyl chain length. We found that phospholipase A2 has considerable activity against N-acetyl PE, but is poorly active against N-butanoyl PE and only marginally active against N-hexanoyl PE, whereas the activity is completely lost when N-hexadecanoyl PE is presented as a substrate. On the other hand, N-hexanoyl PE does not inhibit phospholipase A2 activity, suggesting that this substrate fails to enter the hydrophobic channel. Phospholipase C presents a similar, but less sharp pattern. Molecular dynamics simulations of the polar head group of selected NAPEs reveal a substantially increased conformational variability as the N-acyl chain grows. This larger conformational space represents an increased impairment limiting the access of these molecules to the active site. Our data indicate that, whereas a change in charge contributes to diminished activity, the most relevant effects come from steric hindrance related to the growth of the N-acyl chain.

scholarly journals Different rates of flux through the biosynthetic pathway for long-chain versus very-long-chain sphingolipids

2020 ◽  
Vol 61 (10) ◽  
pp. 1341-1346
Author(s):  
Iris D. Zelnik ◽  
Giora Volpert ◽  
Leena E. Viiri ◽  
Dimple Kauhanen ◽  
Tamar Arazi ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Chain Length ◽  
Biosynthetic Pathway ◽  
Acyl Chain ◽  
Degree Of Saturation ◽  
Disease States ◽  
Acyl Chain Length ◽  
Long Chain Base ◽  
Acyl Chains ◽  
Long Chain

The backbone of all sphingolipids (SLs) is a sphingoid long-chain base (LCB) to which a fatty acid is N-acylated. Considerable variability exists in the chain length and degree of saturation of both of these hydrophobic chains, and recent work has implicated ceramides with different LCBs and N-acyl chains in distinct biological processes; moreover, they may play different roles in disease states and possibly even act as prognostic markers. We now demonstrate that the half-life, or turnover rate, of ceramides containing diverse N-acyl chains is different. By means of a pulse-labeling protocol using stable-isotope, deuterated free fatty acids, and following their incorporation into ceramide and downstream SLs, we show that very-long-chain (VLC) ceramides containing C24:0 or C24:1 fatty acids turn over much more rapidly than long-chain (LC) ceramides containing C16:0 or C18:0 fatty acids due to the more rapid metabolism of the former into VLC sphingomyelin and VLC hexosylceramide. In contrast, d16:1 and d18:1 ceramides show similar rates of turnover, indicating that the length of the sphingoid LCB does not influence the flux of ceramides through the biosynthetic pathway. Together, these data demonstrate that the N-acyl chain length of SLs may not only affect membrane biophysical properties but also influence the rate of metabolism of SLs so as to regulate their levels and perhaps their biological functions.

scholarly journals Effect Of The Acyl Chain Length On The Translocation Rate Of Amphiphilic Molecules In Liquid Disordered And Liquid Ordered Lipid Bilayers

2009 ◽  
Vol 96 (3) ◽  
pp. 351a
Author(s):  
Renato Cardoso ◽  
Filipe M.C. Gomes ◽  
Patrícia T. Martins ◽  
Winchil L.C. Vaz ◽  
Maria J. Moreno
Keyword(s):  
Lipid Bilayers ◽  
Chain Length ◽  
Acyl Chain ◽  
Acyl Chain Length ◽  
Amphiphilic Molecules ◽  
Liquid Ordered

Thermal Properties of Acylated Low Molecular Weight Chitosans

2019 ◽  
Vol 41 (2) ◽  
pp. 207-207
Author(s):  
Shu Xian Tiew and Misni Misran Shu Xian Tiew and Misni Misran
Keyword(s):  
Molecular Weight ◽  
Hydrogen Bonding ◽  
Chain Length ◽  
Acyl Chain ◽  
Low Molecular Weight ◽  
Scanning Electron Micrographs ◽  
Scanning Calorimetry ◽  
Acyl Chain Length ◽  
Medium Chain Length ◽  
Acyl Chains

Acylated low molecular weight chitosans (LChA) were prepared from nucleophilic acylation of chitosan using acid anhydrides of short and medium chain length (4 - 10) to study the response of applied heat as a function of acyl chain length. Thermogravimetric analysis (TGA) revealed the decomposition of LChA consisted of glucosamine and acyl-glucosamine units around 141 - 151and#176;C to 400 - 410and#176;C. Both TGA and differential scanning calorimetry (DSC) analyses indicated that the introduction of acyl groups disrupted the hydrogen bonding of chitosan, the effect was more prominent as the degree of substitution and chain length of LChA increased. Grafting of acyl chains lowered the kinematic viscosity of LChA as the disruption of hydrogen bonding led to decreased hydrodynamic volume. Field emission scanning electron micrographs showed that LChA with longer chains having larger particle size due to bigger occupancy volume of acyl chains during spray drying.

scholarly journals Thermal Conductivity of Polyamide-6,6/Carbon Nanotube Composites: Effects of Tube Diameter and Polymer Linkage between Tubes

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1465 ◽  
Author(s):  
Mahboube Keshtkar ◽  
Nargess Mehdipour ◽  
Hossein Eslami
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Polymer Chains ◽  
Nonequilibrium Molecular Dynamics ◽  
Interfacial Thermal Resistance ◽  
Conductivity Anisotropy ◽  
Nanotube Composites ◽  
Dynamics Simulations ◽  
Effect Of Surface

Reverse nonequilibrium molecular dynamics simulations were done to quantify the effect of the inclusion of carbon nanotubes (CNTs) in the Polyamide-6,6 matrix on the enhancement in the thermal conductivity of polymer. Two types of systems were simulated; systems in which polymer chains were in contact with a single CNT, and those in which polymer chains were in contact with four CNTs, linked together via polymer linkers at different linkage fractions. In both cases, heat transfer in both perpendicular and parallel (to the CNT axis) directions were studied. To examine the effect of surface curvature (area) on the heat transfer between CNT and polymer, systems containing CNTs of various diameters were simulated. We found a large interfacial thermal resistance at the CNT-polymer boundary. The interfacial thermal resistance depends on the surface area of the CNT (lower resistances were seen at the interface of flatter CNTs) and is reduced by linking CNTs together via polymer chains, with the magnitude of the reduction depending on the linkage fraction. The thermal conductivity of polymer in the perpendicular direction depends on the surface proximity; it is lower at closer distances to the CNT surface and converges to the bulk value at distances as large as 2 nm. The chains at the interface of CNT conduct heat more in the parallel than in the perpendicular directions. The magnitude of this thermal conductivity anisotropy reduces with decreasing the CNT diameter and increasing the linkage fraction. Finally, microscopic parameters obtained from simulations were used to investigate macroscopic thermal conductivities of polymer nanocomposites within the framework of effective medium approximation.

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