Surface and micellar properties of some amphiphilic drugs in various salt solutions

In this work the effect adding of various electrolytes on the solution properties of three amphiphilic drugs was investigated. The critical micelle concentration (cmc) values, determined on the basis of surface tension measurements, were found to decrease with the increasing salt concentration; this decrease was dependent upon the nature of added ion. Coions (K⁺ and Na⁺) remained in the aqueous phase and were almost equally efficient in decreasing the cmc. Counterions (Cl^? and Br^?) concentrated on the micellar surface and reduced electrostatic repulsion. The smaller the hydrated counterions, the stronger they interacted with the micellar surface. The decrease of cmc was therefore more pronounced for Br^? ions than that for Cl^? ones. The observed changes in A _min and Γ_max were explained in terms of the cmc behavior. The values of both ΔG _m ^pO and ΔG _ads ^pO suggest that the drugs tend to form micelles more readily in the presence of salts.     

Surface properties of some amphiphilic antidepressant drugs in different aqueous media

Critical micelle concentrations and surface properties of the amphiphilic antidepressant drugs imipramine, clomipramine and desipramine hydrochlorides in different aqueous media, i.e. water and 0.05 mol kg^-1 NaCl and a buffered solution of pH 4.0 and at a temperature of 298.15 K, were determined by surface tension measurements. A mass action model, modified for application to association systems of low aggregation number, was used to calculate the standard Gibbs energy of micellization, \(\Delta G_m^0 \). The standard Gibbs energy of adsorption, \(\Delta G_{ads}^0 \), was also obtained.     

Synthesis of the 3-hydroxy oxiracetam enantiomers, potential nootropic drugs

The enantioselective synthesis of the potentially nootropic compounds 3–6 is reported. Derivative 3 was obtained from the readily available L-tartaric acid, by reduction of the imide 8 prepared with methyl glycinate. The other derivatives 4–6 were obtained from the dihydroxylactam 11. Protection of one of the hydroxyl groups and a Mitsunobu reaction or triflate displacement of the other group produces the remaining stereoisomers. Aminoderivatives 25 and 27 were obtained by displacement with sodium azide and reduction.     

Studies of relationship between polymer structure and hydration environment in amphiphilic polytartaramides

The relationships between the chemical structures and hydration environment of the polymers can provide significant insight into the water‐amphiphilic polymer interactions. Here, the hydrophobicity of amphiphilic block copolymers poly(ethylene tartaramide‐b‐alkyl isocyanate) is gradually tuned by using of a series of pendant alkyl (isopropyl, n‐butyl, cyclopentyl, and cyclohexyl) groups. Dynamics of hydration probed by low‐field NMR relaxometry exhibits a heterogeneous environment of water molecules, corresponding to tightly bound water with slow re‐orientational mobility and loosely bound water with fast re‐orientational mobility. Progressively larger amounts of bound water are present in the copolymers, ongoing from pendant isopropyl, n‐butyl, cyclopentyl, and finally to cyclohexyl group. Water in the copolymer bearing the cyclohexyl group has a significantly high partial specific heat capacity. Therefore, hydrophobic interaction between the polymer and water is enhanced when the hydrophobicity of the polymer is increased, resulting in considerable hydrophobic hydration with decreased mobility of the bound water. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 138–145     

Protein hydration and volumetric properties

Pressure effects on proteins stem from volumetric differences between their conformational states. These differences implicate rigid structure-based solvent excluded void volumes, although hydration and thermal expansivity differences between states may also play a role. Defining quantitatively the contributions of hydration and solvent excluded voids to protein volumetric properties and thermal expansivities remains a major challenge. Experimental information concerning thermal expansivity can be gained from pressure perturbation calorimetric studies (PPC). We review here recent results from PPC that suggest that while hydration plays a significant role in the volumetric properties of unfolded states of proteins, the volumetric properties of folded states are defined by structural and energetic properties of the folded chain.     

Investigation of DNA condensing properties of amphiphilic triblock cationic polymers by atomic force microscopy

Introduction of nucleic acids into cells is an important biotechnology research field which also holds great promise for therapeutic applications. One of the key steps in the gene delivery process is compaction of DNA into nanometric particles. The study of DNA condensing properties of three linear cationic triblock copolymers poly(ethylenimine-b-propylene glycol-b-ethylenimine), namely, LPEI(50)-PPG(36)-LPEI(50), LPEI(19)-PPG(36)-LPEI(19), and LPEI(14)-PPG(68)-LPEI(14), indicates that proper DNA condensation is driven by both the charge and the size of the respective cationic hydrophilic linear polyethylenimine (LPEI) and neutral hydrophobic poly(propylene glycol) (PPG) parts. Atomic force microscopy was used to investigate the interactions of the triblock copolymers with plasmid DNA at the single molecule level and to enlighten the mechanism involved in DNA condensation.     

Synthesis and properties of amphiphilic star polysulfides

We here present the synthesis and characterisation of linear and star-shaped amphiphilic block copolymers based on hydrophobic polysulfides (poly(propylene sulfide), PPS) and hydrophilic polyethers (poly(ethylene glycol), PEG). We also discuss the proof of the principle of their responsiveness to oxidising conditions. In a water environment, these polymers aggregate in the form of sub-micron carriers that, due to the sensitivity to oxidation reactions typical of PPS, can be used for responsive drug delivery. In this first study we have focused on the study of large aggregates, which do not apparently show dramatic differences in behaviour when polymer chains with different degrees of branching are studied.     

Investigation of the crystal structure of two amphiphilic diols

Abstract

The crystal and molecular structures of (R)-4′-(2,3-dihydroxypropyloxy)-4-cyanobiphenyl, 1 and 4′-(cis-cis-3,5-dihydroxycyclohexyloxy)-4-cyanobiphenyl, 5 have been determined. The packing of compound 1 occurs in sheets, with a dense hydrogen bonding network within the layer of one sheet and to the next sheet, whereby the cyano groups are incorporated into the hydrogen bonding network. The hydrogen bonding scheme of compound 5 involves a water molecule; there is some disorder with regard to the hydrogen atoms bound to the water molecules.     

Investigation of the crystal structure of two amphiphilic diols

The crystal and molecular structures of (R)-4'-(2,3-dihydroxypropyloxy)-4-cyanobiphenyl, 1 and 4'-(cis-cis-3,5-dihydroxycyclohexyloxy)-4-cyanobiphenyl, 5 have been determined. The packing of compound 1 occurs in sheets, with a dense hydrogen bonding network within the layer of one sheet and to the next sheet, whereby the cyano groups are incorporated into the hydrogen bonding network. The hydrogen bonding scheme of compound 5 involves a water molecule; there is some disorder with regard to the hydrogen atoms bound to the water molecules.     

Investigation of the effects of diethylene glycol on the hydration of C3S and C3A pastes

The effects of diethylene glycol on the hydration characteristics of tricalcium silicate and tricalcium aluminate pastes were studied. Diethylene glycol acts as a retarder in the hydration of C₃S, and as an accelerator in the hydration of C₃A. The amount of Ca(OH)₂ found in pastes of C₃S treated with diethylene glycol was lower, the induction period increased and the formation of hydrates was retarded. For C₃A pastes, hydration in the presence of diethylene glycol accelerated the formation of the hexagonal aluminate hydrates and promoted the conversion to the cubic form.

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Zusammenfassung Der Einfluss von Diethylenglykol auf die Hydratation von Tricalciumsilicat- (C₃S) und Tricalciumaluminat- (C₃A) -Pasten wurde untersucht. Diethylenglykol verzögert die Hydratation des C₃S und beschleunigt die des C₃A.In C₃S-Proben, die mit Diethylenglykol hydratisiert wurden, ist der Gehalt an Ca(OH)₂ geringer, die Induktionsperiode länger und die Bildung von Hydraten verzögert. In C₃A-Pasten wird in Gegenwart von Diethylenglykol die Bildung des hexagonalen Calciumaluminathydrats beschleunigt und seine Umwandlung in die kubische Form begünstigt.

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The synthesis and photochemical properties of amphiphilic phenylazonaphthalenes

Three novel amphiphilic phenylazonaphthalenes, namely, 6-(4-(4-octylphenylazo)naphthoxy)hexanoic acid, 6-(4-(4-dodecylphenylazo)naphthoxy)hexanoic acid, 6-(4-(4-hexadecylphenylazo)naphthoxy)hexanoic acid, were synthesized by diazo coupling, etherification and hydrolysis reactions successively. The kinetic studies of the trans–cis isomerization indicated that about 95% of the trans isomers of these compounds in chloroform solutions were transformed to cis isomers under the irradiation of near-ultraviolet light (380±30 nm) observed from UV–Vis spectra. In the dark condition, the cis isomers could reversibly convert to trans isomers following the first-order kinetics at the rates of 4.9×10^-4, 5.7×10^-4, 7.7×10^-4 S^-1, respectively.     

Conformational polymorphism and amphiphilic properties of resorcinarene octapodands

o-Nitroaniline functionalized resorcinarene octapodands 1-5 with pendant methyl, ethyl, pentyl, nonyl or 1-decenyl groups, respectively, were synthesized and their structural properties investigated using X-ray crystallography and NMR spectroscopy. The upper rim of each podand is identical containing flexible side arms, in which rotation around the -OCH(2)CH(2)N- linkers create excellent possibilities for polymorphism. Two conformational polymorphs of acetone solvate of 2 were identified containing different side arm orientation and crystal packing. Compound 1 crystallized from acetone and nitromethane yielding two pseudopolymorphs with different packing motifs. The longer alkyl chains of 3-5 lead to differences in solubility and induce amphiphilic properties, which were studied at the air-water interface using the Langmuir-film technique. Crystals of amphiphilic compound 5, which has hydrophobic alkyl tails at the lower rim and hydrophilic nitroaniline groups at the upper rim, showed an interesting packing motif with alternating aromatic and aliphatic layers. Versatile structures of the octapodands in solid state and in solution serve as an example of how conformational flexibility can be utilized in crystal engineering and creating self-assembling monolayer structures.     

Synthesis and properties of an amphiphilic dithiafulvene oligomer

An amphiphilic dithiafulvene oligomer was synthesized by cycloaddition polymerization of aldothioketene generated from 1,4‐diethynylbenzene and a PEO‐grafted phenylacetylene (feed ratio 5/1). The degree of polymerization was determined as 6 by ¹H NMR analysis. The aggregation behavior of the oligomer was studied in the mixed solvent of D₂O and DMSO‐d₆. Effective charge‐transfer interaction of the oligomer and hydrophilic methyl viologen was observed in an aqueous solution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3770–3775, 2007     

Synthesis and properties of amphiphilic maleic acid copolymers

New amphiphilic polymers derived from maleic acid copolymers and containing stearyl or oleyl residues were prepared. Their physicochemical properties were studied, and the possibility of using them as carriers for antifungal agents was examined with Amphotericin B as example.     

Synthesis strategies and properties of smart amphiphilic networks

This paper briefly surveys recent developments in the field of amphiphilic networks (APN) which are a new class of crosslinked polymer systems consisting of covalently bonded hydrophobic and hydrophilic chain segments. The covalent bonds between immiscible hydrophobic and hydrophilic polymer chains prevent demixing and yield polymer networks with unique structure and properties. Telechelic macromonomers provide the basis for the first generation of APNs obtained by copolymerization of the macromonomer with selected low molecular weight monomers. Synthesis of a variety of APNs using methacrylate-telechelic polyisobutylene (PIB) macromonomers prepared by living carbocationic polymerization (LCCP) and quantitative chain end derivatization is reviewed. The second generation of PIB-based amphiphilic networks is prepared by crosslinking of well-defined hydroxy-telechelic PIB and partially deprotected silylated poly(2-hydroxyethyl methacrylate) (PHEMA) precursor chains. Other opportunities providing better structural control of APNs by crosslinking of functional amphiphilic block copolymers (or precursors) obtained by combining living carbocationic and anionic polymerizations are outlined as well. Properties of APNs, such as control of swellability by composition, pH-response of swelling, fast surface structure reorganization by contacting with solvent, morphology, sustained release of drugs and bio- and blood compatibility, are also summarized.     

Volumetric properties, structural effects, and hydration of amino acids in aqueous salt solutions

The dependence of the standard partial volumes of glycine, α-alanine, and serine on the ionic strength of aqueous sodium chloride and sulfate solutions is modeled by the extended Masson equation: {ie534-1}. The error of less than 0.2 cm³/mol is a result of using five values of the A and B parameters: the two values of A are determined by the type of salt and the three values of B by the type of amino acid. A new variation of the additive-group approach is proposed for {ie534-2}. The partial volumes of the CH₃ group (α-alanine) and the CH₂ group (serine) are found not to depend on the salt concentration. The partial volume of the CH₂ group of glycine grows with concentration. The structural characteristics of the hydrated complexes of the NH ₃ ⁺ and COO^? groups are calculated: the hydration numbers, the molar volumes of water inside and outside the hydration sphere, and the intrinsic volume of NH ₃ ⁺ in COO^? in solution. Given the same ionic strength, the aqueous sodium sulfate solution produces a somewhat stronger dehydration of the charged groups.     

Investigation of hydration effects of dibenzodialkyl-18-crown-6 complexes with the potassium ion by the Monte-Carlo method

The hydration of the potassium complexes of dibenzo-18-crown-6, dibenzo-3,12-dibutyl-18-crown-6, and dibenzo-3,12-dioctyl-18-crown-6 has been investigated by the Monte Carlo method. The calculated values of the energies of interaction of water-cation of the metal complex, water -crown ether, and crown ether-cation are pesented. The results of the calculations show that the investigated potassium complexes of the dialkylsubstituted DB18C6 interact with the aqueous phase much more strongly than the potassium complex of DB18C6. This can lead to the additional structurization of the hydrate shell and, as a result of this, to a decrease in S⁰ of complex formation and in the stability of the complexes with the increasing number of CH₂ groups in the alkyl derivatives of DB18C6.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 2, pp. 238–241, March–April, 1990.     

The difference among the effects of high-temperature curing on the early hydration properties of different cementitious systems

The difference among the effects of high-temperature curing on the early hydration properties of the pure cement, the binder containing fly ash, the binder containing GGBS, and the binder containing steel slag was investigated by determining the compressive strength, non-evaporable water content, hydration heat, and Ca(OH)₂ content. Results show that the order of the influence degrees of high-temperature on the early hydration of different binders is the binder containing GGBS > the binder containing steel slag > the binder containing fly ash > the pure cement. In the case of short period of high-temperature curing (only 1 day), the strength growth rate of the concrete containing GGBS is the greatest. Though the influence of increasing high-temperature curing period on the hydration degree of the binder containing fly ash is not the most significant, the strength growth rate of the concrete containing fly ash is the most significant due to the excessive consumption of Ca(OH)₂ by reaction of fly ash. In the case of high-temperature curing, the Ca(OH)₂ content of the paste containing steel slag is much higher than those of the paste containing GGBS and the paste containing fly ash, so though high-temperature curing promotes the hydration of the binder containing steel slag significantly, its influence on the strength growth rate of the concrete containing steel slag is not so significant.     

The mode of association of amphiphilic drugs in aqueous solution

The structural features of amphiphilic drug molecules which influence their association pattern in aqueous solution are identified from a survey of published work. Flexibility of the hydrophobic group, as in the large number of drugs with a diphenylmethane structure, leads to a closed or micellar association. Drugs possessing a rigid planar aromatic or heteroaromatic ring system to which an ester group or charge-bearing N atom is directly attached or which include a pyridine-like N atom, have an open or continuous association pattern. Several association models used to describe the association of these drugs are reviewed. The self-association of the large group of tranquillising drugs which have their charge localised at the end of a short side chain attached to a phenothiazine ring system is discussed in detail. The association pattern in water and dilute electrolyte is complex with discontinuities in solution properties at several critical concentrations. Evidence from a variety of experimental techniques indicates limited association in dilute solution leading to the formation of a stable aggregate at the first critical concentration. NMR studies of the changes in the chemical shifts of aromatic protons and carbon atoms over a wide concentration range have suggested an offset, concave-to-convex vertical stacking of the molecules within these aggregates, with the alkyl side chains on alternate sides of the stack. The association of several phenothiazines in the presence of high concentrations of added electrolyte (0.2 to 0.8 mol kg⁻¹ sodium chloride) has been described by an association scheme in which a primary unit of 3 to 4 monomers is formed below the critical concentration by a continuous association process and grows with increasing solution concentration by the stepwise addition of monomers.