Solid-liquid phase behavior of binary fatty acid mixtures 3. Mixtures of oleic acid with capric acid (decanoic acid) and caprylic acid (octanoic acid)

Solid-liquid phase behavior of binary mixtures of oleic acid (OA)/capric acid (C10A) and OA/caprylic acid (C8A) were investigated by means of differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction. The phase diagram of OA/C10A mixture constructed from the DSC results suggested that a molecular compound with the composition of OA:C10A = 3:2 is formed in a solid phase, and OA and the molecular compound are miscible, while C10A and the molecular compound are completely immiscible. The formation of the molecular compound was supported by the IR spectroscopic observation, and a possible model of the structure was proposed on the basis of X-ray diffraction spectrum in small angle region. This compound formation is characteristic of the OA/C10A mixture, and may be attributed to the similarity of the acyl chain length of C10A to the lengths of Delta- and omega-chains of OA (i.e., the chain segments divided by cis-double bond). The mixture of OA and C8A, whose chain length is close to but shorter than the two chain segments of OA, provided a eutectic-type phase diagram showing a partial mixing of the two components in OA-rich region. Thermodynamic analysis of the liquidus line in the phase diagram exhibits a systematic trend for the non-ideality parameter of mixing with the variation of the chain length difference between OA and saturated fatty acid species.     

Poly(L-lysyl-L-alanyl-alpha-L-glutamic acid). II. Conformational studies.

The solution characterization of poly(Lys-Ala-Glu) is described. This polytripeptide is zwitterionic at neutral pH and is shown to take on a conformation which is dictated by the state of ionization, molecular weight, temperature, and solvent. The polypeptide is almost entirely α-helical at low pH and temperature for polymers of greater than 25,000 molecular weight. Melting profiles for these conditions show t_m ～ 20°C. Analysis of circular dichroism curves shows the α-helical content to vary in a linear manner with molecular weight in the range 3000–30,000. At neutral pH the charged polypeptide is essentially random, but substantial α-helix could be induced by addition of methanol or trifluoroethanol. At temperatures where the sequential polypeptide is a random coil, addition of trifluoroethanol produces a polymer which is mostly α-helical but also contains an appreciable ammount of β-structure. The infrared spectrum of a low-molecular-weight fraction assumed to be cyclo(Lys-Ala-Glu)₂ was tentatively assigned a β-pleated sheet structure. A comparison of this polytripeptide in various ionization states with other polytripeptides containing L -alanine and L -glutamate or L -lysine shows the α-helix directing properties for the (uncharged) residues to lie in the order Ala > Glu > Lys.     

Polynucleotides. XLIV. Synthesis and properties of poly (2-azaadenylic acid) and poly(2-azainosinic acid).

Chemically synthesized 2-azaadenosine 5'-diphosphate (n2ADP) and 2-azainosine 5'-diphosphate (n2IDP) were polymerized to yield poly(2-azaadenylic acid), poly(n2A), and poly(2-azainosinic acid), poly(n2I), using Escherichia coli polynucleotide phosphorylase. In neutral solution, poly(n2A) and poly(n2I) had hypochromicities of 32 and 5.5%, respectively. Poly(n2A) formed an ordered structure, which had a melting temperature (Rm) of 20 degrees C at 0.15 M salt concentration. Upon mixing with poly(U), poly(n2A) formed a 1 : 2 complex with Tm of 41 degrees C at 0.15 M salt concentration. Poly(n2A) and poly(n2I) formed three-stranded complexes with poly(I), and poly(A), respectively. Poly(n2A) . 2poly(I), poly(A) . 2poly(n2I), and poly(n2A) . 2poly(n2I) complexes had Tm values of 23, 48, and 31 degrees C at 0.15 M salt concentration, respectively. Poly(n2I) formed a double-stranded complex with poly(C), but its Tm was very low.     

Biodegradation of copoly(L-aspartic acid/L-glutamic acid) in vitro.

The preparation of copolypeptides consisting of L-aspartic acid and L-glutamic acid was performed to determine the effects of copolymer composition and sequential distributions on the rate of degradation by papain in a PECF (pseudoextracellular fluid) at pH 4.75 and 7.40, at 37.0 degrees C, to simulate in vivo polymer degradation. Random copolymers consisting of beta-benzyl L-aspartate and gamma-benzyl L-glutamate were synthesized by the N-carboxyanhydride method. Water-soluble copolymers were obtained by successive reactions of side chains by anhydrous HBr treatment. All the samples were found to be degraded by random chain scission with papain. Further, the degradation data for the samples followed the Michaelis-Menten rate law, being the first order in papain concentration. The nature of side chains are important to the rate of degradation by papain and it was controlled by the comonomer composition as well as the sequential distribution of comonomers in the copolymer chains.     

The mechanism underlying the hypolipemic effect of perfluorooctanoic acid (PFOA), perfluorooctane sulphonic acid (PFOSA) and clofibric acid.

The influence of the peroxisomal proliferators perfluorooctanoic acid (PFOA), perfluorooctane sulphonic acid (PFOSA) and clofibric acid on lipid metabolism in rats was studied. Dietary treatment of male Wistar rats with these three compounds resulted in rapid and pronounced reduction in both cholesterol and triacylglycerols in serum. The concentration of liver triacylglycerols was increased by about 300% by PFOSA. Free cholesterol was increased by both perfluoro compounds. Cholesteryl ester was reduced to 50% by PFOSA as well by clofibrate. In hepatocytes from fed rats, all the compounds resulted in reduced cholesterol synthesis from acetate, pyruvate and hydroxymethyl glutarate, but there was no reduction of synthesis from mevalonic acid. The oxidation of palmitate was also increased in all groups. The perfluoro compounds, but not clofibrate, caused some reduction in fatty acid synthesis. The activity of liver HMG-CoA reductase was reduced to 50% or less in all treatment groups and all three compounds led to lower activity of acyl-CoA:cholesterol acyltransferase (ACAT). Changes in other enzymes related to lipid metabolism were inconsistent. The present data suggest that the hypolipemic effect of these compounds may, at least partly, be mediated via a common mechanism; impaired production of lipoprotein particles due to reduced synthesis and esterification of cholesterol together with enhanced oxidation of fatty acids in the liver.     

Poly(glutamic acid) for biomedical applications.

Paclitaxel is a widely used anti-cancer agent. Conjugates of paclitaxel with poly(glutamic acid) have shown great promise in preclinical trials, and clinical trials are now underway. Preclinical data suggest that more paclitaxel is preferentially delivered to tumor sites vs. nonconjugated paclitaxel. When poly(glutamic acid) is conjugated to other families of cancer drugs, similar improvements in effectiveness and reduced toxicity are observed. Optimization of poly(glutamic acid) for use in drug delivery applications is a key step in making this technology viable.     

Elongation of (omega-14C)oleic acid and (omega-14C)nervonic acid.

During feeding experiments with [omega-14C]oleic acid and [omega-14c]nervonic acid to adult rats, 14C-labelled C26, C28 and C30 fatty acids were recovered from the intestinal mucosa, liver, plasma, kidney and stools. The structures of these fatty acids were determined by g.l.c., radio-g.l.c. and mass spectrometry. The Schmidt and Ginger degradation methods indicated that most of the 14C found in these extra-long fatty acids remained in the omega position. These radioactive extra-long fatty acids were found mainly in the polar lipids of rats killed 3 or 15 h after being fed on labelled oleic acid or nervonic acid. Rats killed 63 h later yielded only traces of these extra-long fatty acids. When the rats were given antibiotics or received the same radioactive fatty acids by intravenous injection, the labelled extra-long fatty acids could not be detected in any of the tissues. We conclude that they were probably synthesized by elongation of oleic acid and nervonic acid by intestinal micro-organisms (probably yeasts) and then absorbed by the intestinal mucosa.     

A linoleic acid (8R)-dioxygenase and hydroperoxide isomerase of the fungus Gaeumannomyces graminis. Biosynthesis of (8R)-hydroxylinoleic acid and (7S,8S)-dihydroxylinoleic acid from (8R)-hydroperoxylinoleic acid.

The fungus Gaeumannomyces graminis metabolized linoleic acid extensively to (8R)-hydroperoxylinoleic acid, (8R)-hydroxylinoleic acid, and threo-(7S,8S)-dihydroxylinoleic acid. When G. graminis was incubated with linoleic acid under an atmosphere of oxygen-18, the isotope was incorporated into (8R)-hydroxylinoleic acid and 7,8-dihydroxylinoleic acid. The two hydroxyls of the latter contained either two oxygen-18 or two oxygen-16 atoms, whereas a molecular species that contained both oxygen isotopes was formed in negligible amounts. Glutathione peroxidase inhibited the biosynthesis of 7,8-dihydroxylinoleic acid. These findings demonstrated that the diol was formed from (8R)-hydroperoxylinoleic acid by intramolecular hydroxylation at carbon 7, catalyzed by a hydroperoxide isomerase. The (8R)-dioxygenase appeared to metabolize substrates with a saturated carboxylic side chain and a 9Z-double bond. G. graminis also formed omega 2- and omega 3-hydroxy metabolites of the fatty acids. In addition, linoleic acid was converted to small amounts of nearly (65% R) racemic 10-hydroxy-8,12-octadecadienoic acid by incorporation of atmospheric oxygen. An unstable metabolite, 11-hydroxylinoleic acid, could also be isolated as well as (13R,13S)-hydroxy-(9E,9Z), (11E)-octadecadienoic acids and (9R,9S)-hydroxy-(10E), (12E,12Z)-octadecadienoic acids. In summary, G. graminis contains a prominent linoleic acid (8R)-dioxygenase, which differs from the lipoxygenase family of dioxygenases by catalyzing the formation of a hydroperoxide without affecting the double bonds of the substrate.     

Stabilization of (90)y-labeled DOTA-biomolecule conjugates using gentisic acid and ascorbic acid.

Radiolytic degradation of radiolabeled compounds is a major challenge for the development of new therapeutic radiopharmaceuticals. The goal of this study is to explore the factors influencing the solution stability of a (90)Y-labeled DOTA-peptide conjugate (RP697), including the amount of total activity, the activity concentration, the stabilizer concentration, and the storage temperature. In general, the rate of radiolytic decomposition of RP697 is much slower at the lower activity concentration (<4 mCi/mL) than that at the higher concentration (>10 mCi/mL). RP697 remains relatively stable at the 20 mCi level and room temperature while it decomposes rapidly at the 100 mCi level under the same storage conditions. Radical scavengers, such as gentisic acid (GA) and ascorbic acid (AA), were used in combination with the low temperature (-78 degrees C) to prevent the radiolytic decomposition of RP697. It was found that RP697 remains stable for at least 2 half-lives of (90)Y when GA or AA (10 mg for 20 mCi of (90)Y) is used as a stabilizer when the radiopharmaceutical composition is stored at -78 degrees C. The stabilizer (GA and AA) can be added into the formulation either before or after radiolabeling. The post-labeling approach is particularly useful when the use of a large amount of the stabilizer interferes with the radiolabeling. The radiopharmaceutical composition developed in this study can also apply to other (90)Y-labeled DOTA-biomolecule conjugates. The amount of the stabilizer used in the radiopharmaceutical composition and storage temperature should be adjusted according to the sensitivity of the radiolabeled DOTA-biomolecule conjugate toward radiolytic decomposition.     

Synthesis and characterization of 1,1,4,4-butanetetracarboxylic acid. A di-gamma-carboxyglutamic acid (GlaGla) analogue

1,1,4,4-Butanetetracarboxylic acid (BTCA) is evaluated as an analogue for the metal binding site in dipeptides of gamma-carboxyglutamic acid (Gla). Molecular modeling suggests that the four carboxylic acid groups in BTCA can assume a similar conformation to the four gamma-carboxylic acid groups in GlaGla and thus provides the impetus for the synthesis and metal binding determinations. BTCA is synthesized via the tert.-butyl ester and characterized via NMR, mass spectroscopy, and elemental composition. Equilibrium binding constants with protons, Ca(II) and Mg(II) are determined via pH and Ca(II) ion-selective electrode titrations and are found to be similar to those for GlaGla peptides with blocked termini.