Thermal Properties of Acylated Low Molecular Weight Chitosans

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.

Download Full-text

Effect of Acyl Chain Length and Unsaturation on Physicochemical Properties and Transfection Efficiency of N-Acyl-Substituted Low-Molecular-Weight Chitosan

Journal of Pharmaceutical Sciences ◽

10.1002/jps.22767 ◽

2012 ◽

Vol 101 (1) ◽

pp. 268-282 ◽

Cited By ~ 11

Author(s):

Rhishikesh Mandke ◽

Jagdish Singh

Keyword(s):

Molecular Weight ◽

Physicochemical Properties ◽

Chain Length ◽

Transfection Efficiency ◽

Acyl Chain ◽

Low Molecular Weight ◽

Acyl Chain Length ◽

Low Molecular Weight Chitosan

Download Full-text

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

Biochemical Journal ◽

10.1042/bj1880585 ◽

1980 ◽

Vol 188 (3) ◽

pp. 585-592 ◽

Cited By ~ 8

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.

Download Full-text

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

ASME/JSME 2011 8th Thermal Engineering Joint Conference ◽

10.1115/ajtec2011-44465 ◽

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.

Download Full-text

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

The Journal of Lipid Research ◽

10.1194/jlr.ra120000984 ◽

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.

Download Full-text