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At least 19 recordsLinked to original sources
PubMed2005

Hydrogen bonding and the inductive effect in crystalline and solution phases of hexylamine:LiCF3SO3 and Dipropylamine:LiCF3SO3: application to branched poly(ethylenimine).

Raman and infrared spectroscopy were used to study the nature of hydrogen bonding and the cation inductive effect in solutions of LiCF(3)SO(3) dissolved in hexylamine, a primary amine, and dipropylamine, a secondary amine. Comparison of pure hexylamine and hexylamine dissolved in CCl(4) established that the Raman band maximum of the symmetric stretching mode, nu(s)(NH(2)), in pure hexylamine originates in molecules undergoing no hydrogen bonding interactions. The addition of LiCF(3)SO(3) to hexylamine or dipropylamine shifts the frequencies of the solvent NH stretching modes by two effects: the breaking of hydrogen bonds and the cation inductive effect. Comparison of the infrared and Raman spectra allows (to some degree) the separation of these two effects. During these studies, crystalline compounds of hexylamine:LiCF(3)SO(3) and dipropylamine:LiCF(3)SO(3) were discovered, and their structures were solved by single-crystal X-ray diffraction techniques. Vibrational spectra of these crystals and detailed structural knowledge of the cation-solvent interactions complement analogous spectroscopic studies of the solution phases. The cation-polymer and hydrogen bonding interactions of branched poly(ethylenimine) (BPEI) complexed with LiCF(3)SO(3) were modeled by the solutions of hexylamine and dipropylamine containing dissolved LiCF(3)SO(3). Specifically, lithium ion interactions with the primary and secondary amine groups in BPEI were modeled by the solution studies with hexylamine and dipropylamine, respectively. The analysis of the hexylamine system was particularly useful because the primary amine group of BPEI dominates the NH stretching region of the spectrum.

Journal Article↗
PubMed1999

Intercalation of Hexylamine into Hydrated Kaolinite Phenylphosphonate.

Hydrated kaolinite phenylphosphonate (KPP-hyd) was reacted with hexylamine under ambient conditions. The reaction produced a stable light-yellow compound (KPP-hex) that was isolated and characterized by X-ray diffraction, thermal methods (simultaneous thermogravimetric and differential scanning calorimetric analysis), Fourier transform infrared spectroscopy, and elemental CHN analysis. The increase in the interlayer distance from 15.02 to 16.36 Å on going from KPP-hyd to KPP-hex was attributed to the replacement of water molecules with the longer hexylamine molecules in the phenylphosphonate P-O-H binding sites of the grafted KPP host. Upon heating, the phase KPP-hex release the hexylamine molecules that burn. The resulting KPP-dry is stable up to 498 degrees C, at which temperature the grafted phenylphosphonate begins to burn and the dehydroxilation of kaolinite takes place. Copyright 1999 Academic Press.

Journal Article↗
PubMed1986

Study of the hydrolysis and ionization constants of Schiff base from pyridoxal 5'-phosphate and n-hexylamine in partially aqueous solvents. An application to phosphorylase b.

Formation and hydrolysis rate constants as well as equilibrium constants of the Schiff base derived from pyridoxal 5'-phosphate and n-hexylamine were determined between pH 3.5 and 7.5 in ethanol/water mixtures (3:17, v/v, and 49:1, v/v). The results indicate that solvent polarity scarcely alters the values of these constants but that they are dependent on the pH. Spectrophotometric titration of this Schiff base was also carried out. We found that a pKa value of 6.1, attributed in high-polarity media to protonation of the pyridine nitrogen atom, is independent of solvent polarity, whereas the pKa of the monoprotonated form of the imine falls from 12.5 in ethanol/water (3:17) to 11.3 in ethanol/water (49:1). Fitting of the experimental results for the hydrolysis to a theoretical model indicates the existence of a group with a pKa value of 6.1 that is crucial in the variation of kinetic constant of hydrolysis with pH. Studies of the reactivity of the coenzyme (pyridoxal 5'-phosphate) of glycogen phosphorylase b with hydroxylamine show that this reaction only occurs when the pH value of solution is below 6.5 and the hydrolysis of imine bond has started. We propose that the decrease in activity of phosphorylase b when the pH value is less than 6.2 must be caused by the cleavage of enzyme-coenzyme binding and that this may be related with protonation of the pyridine nitrogen atom of pyridoxal 5'-phosphate.

Amines↗
PubMed1994

Photophysical study of the Schiff bases of 5'-deoxypyridoxal and n-hexylamine in cationic micelles.

The absorption and fluorescence spectra of the Schiff bases formed between 5'-deoxypyridoxal and n-hexylamine in aqueous media containing different concentrations of the cationic surfactant hexadecyltrimethylammonium bromide were recorded at 25 degrees C. The quantum yields of fluorescence of the different zwitterionic and enol forms of the chemical species of the Schiff bases occurring in media of pH 4.5-8.5 were determined. Also, the fluorescence quenching resulting from the presence of the surfactant and that of iodide ion were analyzed. From the results obtained it follows that the zwitterionic forms do not interact with the cationic surfactant, whereas the enol forms do interact with it.

Amines↗
PubMed1993

Formation of a new 1,1,1 adduct in the reaction of malondialdehyde, n-hexylamine and alkanal under neutral conditions.

The reactions of malondialdehyde (MDA) with n-hexylamine (HA) in the presence of alkanals at a neutral pH were investigated. Two new compounds, 1,1,1 adduct (4a) and fluorescent compound (3a), were isolated from the reaction of MDA, HA and acetaldehyde. Compounds 4a and 3a were identified as 2-formyl-3-hexylamino-3-methylpropanal and 1-hexyl-5-hexyliminomethylene-4-methyl-1,4-dihydropyridine-3-carba ldehyde, respectively. Similar compounds (4b and 3b) were obtained from the reaction of MDA, HA and propanal. Compound 4 was obtained in a high yield. In addition, the reactivity of MDA towards phenylethylamine (PEA) in the presence or absence of alkanals was investigated. The results indicated that MDA was of low reactivity in the absence of alkanals at neutral pH. However, when alkanals coexisted, MDA showed high reactivity towards PEA.

Aldehydes↗
PubMed1999

Improved RPLC determination of acyclovir using hexylamine as silanol masking agent.

The aim of the present work is to improve the sensitivity in the RPLC determination of acyclovir [9-(2-hydroxy ethoxymethyl) guanine] (ACV) and guanine, the major impurity of the drug synthesis and one of the compounds found in the chemical degradation process of ACV. The method was applied to the quantification of drug in liposomal formulations. The most important problem for RPLC analysis of both compounds are their high pKa values, mainly guanine, and the interaction with reactive silanol groups in the stationary phase. In order to avoid these problems there are four basic strategies: (i) ionic pair reagents, (ii) deactivated silica columns, (iii) polymeric based columns and (iv) silanol masking agents. A validation protocol was followed to develop the analytical method, using a Spherisorb ODS (250 x 4.6 mm i.d.) analytical column, with a mobile phase of 95% aqueous phosphate buffer (pH 3.0) and 5% HPLC methanol pumped isocratically at 1.3 ml/min(-1), with ultraviolet detection at 254 nm. The results showed a high reproducibility in retention time value, with R.S.D. of 2.37% for ACV and 0.32% for guanine. The lowest concentration levels assayed, 0.15 microg/ml(-1) for guanine and 1 microg/ml(-1) for ACV, showed good R.S.D. in the quantification parameter (peak area) 11.0% (guanine) and 9.64% (ACV)

Acyclovir↗
PubMed1991

Biological microemulsions: Part III--The formation characteristics and transport properties of saffola-aerosol OT-hexylamine-water system.

The results of formation, phase behaviour and physical properties of biological microemulsions prepared from saffola/AOT/hexylamine/water in presence of different additives, viz. cholesterol, crown ether, urea and brine, are presented. It has been found that the additives and temperature have striking effects; mono-, bi- and triphasic solutions interchanging proportions among themselves. The conduction of microemulsion at different [Water/AOT] ratios (w = 9,10,14,18,20,39 and 45) has shown conspicuous dependence on temperature with a significant degree of percolation, whereas the dependence of viscosity on temperature has shown normal declining trend with temperature. A maximum in viscosity with respect to its variation with amount of water has been observed. The Walden product (lambda eta) has evidenced noncompensation of ion transport by conduction with the viscosity of the medium. The activation energies evaluated for conduction (delta E*cond) and viscosity (delta E*vis) are systematic except at [Water/AOT] ratio, w = 20. The additives cholesterol, crown ether and their mixture have shown a decreasing effect on the delta E*cond for percolation, whereas delta E*vis has increased in their presence. The bicontinuous microemulsion has the prospect for use as liquid membrane.

Aerosols↗
PubMed2002

Application of 1-alkylamines to a liquid chromatographic/turbo ionspray tandem mass spectrometric method for quantifying metabolites of a new bone anabolic agent, TAK-778, in human serum.

We investigated the application of alkylamines, as additives to the mobile phase, to a quantification method for the metabolites, M-III and M-IV, of TAK-778, which is a new bone anabolic agent, in human serum using liquid chromatography/tandem mass spectrometry (LC/MS/MS). Prior to setting up the analytical method, we found that 1-alkylamines co-existing with M-III and M-IV in the turbo ionsprayed solution formed 1-alkylammonium adduct molecules of these metabolites during the ionization process, and the abundance of the adduct ions was considerably higher than that of protonated molecules ([M + H](+)s) of these metabolites. Based on these findings, we investigated a variety of 1-alkylamines and their spiked concentrations in the mobile phase for LC/MS/MS analysis to obtain higher sensitivities for the quantification of these metabolites. After these examinations, we found that 1-hexylamine at a final concentration of 0.05 mmol l(-1) was the most suitable additive for the mobile phase, and set the selected reaction monitoring (SRM) ions for the 1-hexylammonium adduct molecule and [M + H](+), allowing about a fivefold gain in the SRM chromatographic peak compared with that without 1-hexylamine. The adduct ion was considered to be formed by interaction between the amino group of 1-hexylamine and the phosphoryl group of M-III and M-IV. The internal standard (I.S.) used was deuterated M-III for each metabolite. The analytes and I.S. were extracted with diethyl ether from serum samples at neutral pH and injected into the LC/MS/MS system with a turbo ionspray interface. The limit of quantification for both analytes was 0.5 ng ml(-1) when 0.1 ml of serum was used, and the calibration curves were linear in the range 0.5-100 ng ml(-1). The method was precise; the intra- and inter-day precisions of the method were not more than 5.6%. The accuracy of the method was good, with deviations between added and calculated concentrations of M-III and M-IV being typically within 16.6%. This method provided reliable pharmacokinetic data for M-III and M-IV after the intramuscular administration of TAK-778 sustained-release formulation in humans.

Alkylation↗
PubMed1984

Physical model approach in the study of the transport of alkyl amines across a silicone rubber membrane in a two-chamber diffusion cell.

The transport of hexylamine and octylamine through a silicone rubber membrane was studied as a function of buffer (phosphate) concentration and pH. The results were interpreted using a physical model which assumed a steady-state rate of transport and which accounted for the simultaneous diffusion and rapid equilibrium of all the aqueous species, the possible diffusion of both the amine and its protonated form through the membrane, and the effect of a stagnant aqueous diffusion layer on each side of the membrane. The following conclusions were reached: The thickness of the aqueous diffusion layer is approximately 100 micron, which is about the same as that previously measured for benzoic acid in this system. Transport of octylamine at pH greater than or equal to 10 is approximately 90% aqueous diffusion layer controlled, whereas hexylamine is approximately 50% aqueous diffusion layer controlled at high pH. The membrane permeability of octylamine is approximately 15-20 times that of hexylamine. This gives an incremental pi constant for the partition coefficient of approximately 0.61, as compared with the previously reported value of 0.56. At low pH (less than or equal to 5), the transport of the protonated species becomes important. The membrane permeabilities of these ammonium ions are about four or five orders of magnitude less than the membrane permeabilities of the corresponding amines. The membranes were examined at 30,000X with the scanning electron microscope, and no evidence of holes was found.

Amines↗
PubMed2006

Enhanced skin permeation of salicylate by ion-pair formation in non-aqueous vehicle and further enhancement by ethanol and l-menthol.

Enhancement of skin permeability of salicylate from non-aqueous vehicle by ion-pair formation with either alkylamines or benzylamine as model cationic ions was examined in excised guinea pig dorsal skin. Solubility of salicylate in isopropyl myristate (IPM) was increased by the addition of either alkylamines or benzylamine as counter ions. The increase was more significant in the presence of amines with longer alkyl chains. Flux of salicylate increased in the presence of these amines due to the increase in the solubility. Maximum flux was observed in the presence of n-hexylamine, which induced an 11-fold increase due to 137-fold increase in solubility. Flux and permeability coefficients of salicylate in the presence of n-butylamine, n-hexylamine, iso-octylamine and benzylamine as counter ions in IPM were larger than those of the non-ionic form of salicylic acid. Flux of 3-methylsalicylate (3-CH3 substituent) and that of 5-hydroxysalicylate (5-OH substituent) were smaller than that of salicylate in the presence of n-hexylamine. After partition to the skin surface, the ion-pair is suggested to dissociate and permeate separately according to the study using lidocaine as the counter ion. Flux of salicylate increased in the presence of benzylamine as the counter ion by the addition of 15% ethanol and 15% ethanol plus 1% l-menthol due to further improvement in the solubility as well as an increase in the permeability coefficient.

Administration, Cutaneous↗
PubMed2005

Simultaneous spectrophotometric analysis of aliphatic amines utilizing thermochromism of charge-transfer complexes with tetrabromophenolphthalein ethyl ester.

Aliphatic amines, such as n-hexylamine (primary), di-n-hexylamine (secondary) and tri-n-hexylamine (tertiary amine), react with tetrabromophenolphthalein ethyl ester molecules (TBPEH) to form reddish or red-violet charge-transfer complexes (CT complexes) in 1,2-dichloroethane (DCE). The absorption maxima of the CT complexes with all primary amines occur at around 560 nm, with secondary amines at 570 nm and, with tertiary amines at 580 nm. The CT complex formation constants with TBPEH in DCE increase in the order of the primary, secondary and tertiary amines, but their constants decrease quantitatively with an increase in temperature. This phenomenon (thermochromism) could be applied to the simultaneous spectrophotometric determination of primary amine and secondary amine, or secondary amine and tertiary amine in a mixed solution utilizing the difference of absorbance with temperature changes.

Journal Article↗
PubMed1976

Quantitative relationships between phosphorylation, electron flow, and internal hydrogen ion concentrations in spinach chloroplasts.

1. Further evidence that the uptake of [14C]hexylamine, determined by centrifugal filtration of spinach chloroplast thylakoids through silicone fluid layers, gives precise estimations of light-induced H+ concentration gradients (deltapH) is presented. DeltapH was independent of the amount of thylakoids used or of the concentration of hexylamine. Moreover, hexylamine uptake was sensitive to the osmolarity of the suspending medium. 2. Internal H+ concentration ([H+]in) is proportional to the rate of electron flow when light intensity was used to vary these parameters. Proportionality was still observed in the presence of 0.1 and 1.0 muM gramicidin D. When, however, [H+]in and electron flow were varied by increasing the concentration of gramicidin D, at constant light intensity the rate of electron flow was approximately proportional to 1/[H]in. 3. The phosphorylation efficiency (P/e2 ratio) falls with decreasing light intensity or increasing concentrations of the phosphorylation inhibitor, 4'-deoxyphlorizin. The proportionality between the rate of electron flow and [H+]in allows the calculation of the rate of nonphosphorylating (basal) electron flow if [H+]in under phosphorylating conditions is known. The contribution of basal electron flow, a consequence of passive efflux of H+ from the thylakoids, to the overall rate of electron flow increases as the rate of phosphorylation decreases. P/e2 ratios calculated using rates of electron flow from which the basal component has been subtracted are constant. A calculated P/e2 ratio of about 1.3 is obtained. 4. It is shown that the reciprocal of the phosphorylation efficiency should be proportional to 1/[H+]in2 when these parameters are varied using light intensity. This relationship was verified and provided an estimate of the P/e2 at infinite [H+]in. This value was 1.3. These results provide further evidence that a H+ electrochemical gradient serves to couple photophosphorylation to electron flow and that the rate of phosphorylation is proportional to [H+]in3. That is, three H+ are translocated out of thylakoids for each adenosine triphosphate formed.

Chlorophyll↗
PubMedDate not supplied

Effect of aliphatic monoamines on motor activity of mice: no direct interaction with dopaminergic D2 receptor.

The effect of butylamine, pentylamine and hexylamine on spontaneous locomotor activity of mice was evaluated in the presence or absence of drugs affecting monoaminergic neurons. Pentylamine and hexylamine produced similar effects (stimulation after low, inhibition after high doses), while butylamine action was weak. Depression of locomotor activity produced by combined treatment with alpha-methyl-tyrosine, reserpine and dopa was counteracted by pentylamine and hexylamine; they did not produce such an effect in the absence of dopa. The amines did not displace 3H-spiperone specifically bound to striatal membranes.

Amines↗
PubMed2004

Vacancy ion-exclusion/adsorption chromatography of aliphatic amines on a polymethacrylate-based weakly basic anion-exchange column.

Vacancy ion-exclusion/adsorption chromatography has been applied to investigate the separation behavior of five aliphatic amines (ethylamine, propylamine, butylamine, pentylamine and hexylamine) on a polymethacrylate-based weakly basic anion-exchange column (Tosoh TSKgel DEAE-5PW). This system is consisted of analytes as a mobile phase and water as an injected sample. In the vacancy ion-exclusion/adsorption chromatography, the elution order was as follows: ethylamine < propylamine < butylamine < pentylamine < hexylamine, depending on their hydrophobicity. The retention times of the amines were decreased with decreasing their concentrations in the mobile phase. The retention times and resolutions of the amines were increased by adding a basic compound (e.g., lithium hydroxide or heptylamine) and by increasing the pH of mobile phase (pH > 11). This was because the dissociations of amine samples in the mobile phase were suppressed and thus the hydrophobic adsorption effects were enhanced. The linearity of calibration graphs could be obtained from the peak areas of the amine samples injected to the 0.05, 0.5 and 5 mM of amine mobile phase at pH 11 by heptylamine. The detection limits of aliphatic amines as injected samples were around 1 microM for five aliphatic amines at three different amine mobile phases. From these results, the retention behaviors of aliphatic amines on vacancy ion-exclusion/adsorption chromatography were concluded to be governed by the hydrophobic adsorption effect.

Adsorption↗