Association behavior of one-end hydrophobically modified poly[<Emphasis Type="Italic">N</Emphasis><Superscript>5</Superscript>-(2-hydroxyethyl) <Emphasis Type="SmallCaps">l</Emphasis>-glutamine] in water/ethylene glycol mixed solvent

Amphiphilic polymers Cn-PHEG consisting of water-soluble poly[N ⁵-2-(hydroxyethyl) l-glutamine] (PHEG) and hydrophobic alkyl chain (carbon number n = 12, 14, 16, or 18) attached at the PHEG terminal was prepared, and association behavior and structure of associate for Cn-PHEG in selective solvent (water/ethylene glycol mixed solvent) have been investigated. α-Helix content of PHEG block for all the polymers increased with weight fraction of ethylene glycol in the mixed solvent (W _EG). By light scattering measurements, formation of a small micelle was suggested for C14-, C16-, and C18-PHEG when W _EG = 0. With the increase in W _EG, appearance of a larger associate was revealed for C16- and C18-PHEG. Evaluated molecular weight and radius of gyration suggested that the micelle is star-like sphere when W _EG = 0 and worm-like cylinder when W _EG = 0.7. C12-PHEG did not demonstrate any distinct micellization behavior because of the weak hydrophobicity of C12 chain.     

Thermodynamics of the interaction of liquid-crystalline polypropyleneimine dendrimer with low-molecular-weight compounds studied by reversed-phase gas chromatography

The thermodynamic functions of dissolution of n-alkanes (C₇–C₉) and n-alkanols (C₅–C₈) in the liquid-crystalline and isotropic phases of polypropyleneimine dendrimer of the first generation at infinite dilution were determined by the reversed-phase gas chromatography. The dependences of the thermodynamic parameters of sorbates on the phase state of the dendrite solvent, hydrocarbon chain length, and polarity of low-molecular-weight components of mesogenic—nonmesogenic binary systems were considered. The role of dispersion forces and specific intermolecular interactions in the solutions under study was estimated. Saturated hydrocarbons are more compatible with columnar phases of the dendrimer than alcohols.     

Relationships between miscibility behavior and chemical structure of phospholipids in pseudobinary systems

The influence of chain length differences of cephalines and the influence of the head group methylation on the miscibility behavior of N-methylated phosphatidylethanolamine (PE) mixtures in aqueous dispersions were tested. Nine different phase diagrams were studied by means of differential scanning calorimetry. The phase diagrams of the five pseudobinary cephaline/cephaline/water systems (fatty acid chain length: C _n , n = 12–18) showed that in the high temperature L_α phase all the homologous cephalines were completely miscible. In the low-temperature phase a distinct succession of the phase diagram types was observed according to increasing chain length differences of the PEs: complete miscibilty (C₁₂/C₁₄; C₁₄/C₁₆), peritectic mixing behavior (C₁₂/C₁₆; C₁₄/C₁₈), eutectic mixing behavior (C₁₂/C₁₈). Furthermore four phase diagrams of pseudobinary phospholipid systems consisting of N-methylated PEs with different numbers of methyl groups and a constant length of fatty acid chains were investigated and compared. These four phase diagrams showed phase separations in the low-temperatures phase (gel phase). The width and the concentration range of the miscibility gaps changed systematically with increasing degree of methylation of the head group of the mixing components and are connected with different possibilities of PEs to form hydrogen bridges between the mixture components. Received: 26 August 1999/Accepted: 30 August 1999     

A viscometric study of tuning micellar morphology by organic additives

The micellar morphology in aqueous 0.2 M sodium dodecyl sulfate (SDS) solutions has been studied in the simultaneous presence of organic salts (anilinium hydrochloride, AHC; ortho-toluidine hydrochloride, oTHC; para-toluidine hydrochloride, pTHC) and aliphatic alcohols (n-butanol, C₄OH; n-pentanol, C₅OH; n-hexanol, C₆OH; n-heptanol, C₇OH), aliphatic amines (n-butylamine, C₄NH₂; n-pentylamine, C₅NH₂; n-hexylamine, C₆NH₂; n-heptylamine, C₇NH₂), or hydrocarbons (n-hexane, C₆H; n-heptane, C₇H) by viscosity measurements under Newtonian flow conditions at 30 °C. Addition of alcohols and amines causes micellar growth which is found to be dependent upon chain length of the additive and nature of organic salt counterion. It is observed that amines are more effective in increasing the viscosity of the system if added in pure 0.2 M SDS solution, while SDS + pTHC system was found versatile when alcohols were added to this system. The increased viscosity or the micellar growth is explained in terms of the site of solubilization of the respective additive and the interaction of the additive with micellar surface and salt counterion present in the head group region. Hydrocarbons are nearly ineffective in inducing micellar growth and can be used as ‘micellar destroyer’ for the grown micelles. The additives used are found effective in tuning the environment of the micelle which is reflected in viscosity behavior. This work may find use in micellar ultrafiltration as well as in mimicking the natural cell, which has several aspects common with the micelle.     

The equivalence of bond-energy schemes and the determination of resonance energies

 It is argued that the preservation of algebraic equivalence between the Allen and Laidler bond-energy schemes for nonconjugated alkenes logically determines that the Allen scheme should apply to a classical structure of a conjugated hydrocarbon exactly as it stands, i.e. no additional parameters are needed. Extending the requirement of equivalence to conjugated alkenes implies that, in the Laidler scheme, the bond energy of the pure single CC bond in a conjugated system is a combination of the bond-energies of the semiconjugated and normal CC single bonds: E(C_d—C_d)=2E(C_d—C)−E(C—C). This result is a deduction and is not an independent hypothesis. The equivalence of the two schemes for conjugated hydrocarbons is demonstrated numerically, by calculating the resonance energies of some selected molecules by both methods. Received: 5 December 1999 / Accepted: 5 March 2000 / Published online: 5 June 2000     

Investigation of cuticular hydrocarbons from <Emphasis Type="Italic">Bagrada hilaris</Emphasis> genders by SPME/GC-MS

The cuticular hydrocarbons of male and female Bagrada hilaris Burmeister (Heteroptera: Pentatomidae) were investigated, by headspace solid-phase microextraction followed by gas chromatography–mass spectrometry. Measurements were done with fiber coatings of different polarity after optimization of headspace volumes and extraction temperatures. This resulted in the use of polyacrylate fiber, 22-ml vial as the sample holder, and an extraction temperature of 150 °C. The analytical procedures allowed identification of 13 peaks, corresponding to a homologous series of n-alkanes (nC₁₇–nC₂₉). The hydrocarbon profiles of male and female B. hilaris were qualitatively equal, but marked sex-specific quantitative differences were observed for some of the linear alkanes.     

Kinetic regularities of the heat release during the reactions of aliphatic hydrocarbons with aqueous HNO3

The kinetics of the heat release during the reactions of aqueous HNO₃ withn-heptane andn-octadecane was studied. The kinetic regularities of the reactions of hydrocarbons C₇H₁₆−C₁₈H₃₈ with HNO₃ and the heats of the reactions were described. At all stages, except initial, the hydrocarbon reacts with NO₂ and nitric acid reproduces NO₂ in the reaction with NO. The accumulation of NO₂ results in the acceleration of the process. When the pressure of the hydrocarbon vapor is equilibrium, its reaction with NO₂ can also proceed in the gas phase. The contribution of this reaction to the total heat release was estimated. The additives of aromatic and unsaturated hydrocarbons to aliphatic hydrocarbons increase strongly the initial rate of the heat release and changes slightly the subsequent stages of the process. Naphthenic hydrocarbons have almost no effect on the kinetic parameters of the process. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 35–40, January, 1998.     

Cage Structure Formation of Singly Doped Aluminum Cluster Cations Al<Subscript><Emphasis Type="BoldItalic">n</Emphasis></Subscript><Emphasis Type="BoldItalic">TM</Emphasis><Superscript>+</Superscript> (<Emphasis Type="BoldItalic">TM</Emphasis> = Ti,V, Cr)

Structural information on free transition metal doped aluminum clusters, Al _n TM ⁺ (TM = Ti, V, Cr), was obtained by studying their ability for argon physisorption. Systematic size (n = 5 – 35) and temperature (T = 145 – 300 K) dependent investigations reveal that bare Al _n ⁺ clusters are inert toward argon, while Al _n TM ⁺ clusters attach one argon atom up to a critical cluster size. This size is interpreted as the geometrical transition from surface-located dopant atoms to endohedrally doped aluminum clusters with the transition metal atom residing in an aluminum cage. The critical size, n _crit , is found to be surprisingly large, namely n _crit = 16 and n _crit = 19 – 21 for TM = V, Cr, and TM = Ti, respectively. Experimental cluster–argon bond dissociation energies have been derived as function of cluster size from equilibrium mass spectra and are in the 0.1–0.3 eV range.     

Inertness of C<Subscript>60</Subscript> fullerene toward RO<Subscript>2</Subscript><Superscript>·</Superscript> peroxy radicals

The reactivity of fullerene C₆₀ toward peroxy radicals RO₂ ^· was tested by the chemiluminescence method. A comparison of the influence of C₆₀ and known inhibitors on the kinetics of liquid-phase chemiluminescence (CL) during oxidation of a series of hydrocarbons (ethyl-benzene, cyclohexane, n-dodecane, and oleic acid) shows that the fullerene does not react with the RO₂ ^· radicals. A sharp decrease in the CL intensity observed upon C₆₀ addition is caused by the quenching of CL emitters with fullerene but not by inhibition of hydrocarbon oxidation. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1808–1811, August, 2005.     

Positive ion–molecule reactions in OCS/hydrocarbon mixtures

The positive ion–molecule reactions of OCS have been investigated in an ion cyclotron resonance spectrometer. A variety of reactions in OCS/hydrocarbon mixtures have been investigated for various C₁? C₄ hydrocarbons—alkanes, alkenes and alkynes. The formation of organosulfur ions is found in reactions in OCS/hydrocarbon (C_n) mixtures with n <4. Formation of organosulfur ions is observed from hydrocarbon ions reacting with OCS and [OCS]⁺˙ and S⁺˙ reacting with the hydrocarbons. The proton affinity of OCS has been determined to be 688.7±8 kJ mol^?1 while that of CS₂ is measured to be 712.1±8 kJ mol^?1. Comparison with the proton affinity of CO₂ shows that the proton affinity increases as sulfur is substituted for oxygen.     

Structure and stability of hypervalent NLi n Na2 (n = 1–4) and related species at density functional theory level

A number of configurations of NLi _n Na₂ (n = 1–4) species were optimized using the B3LYP–density functional theory method; the 6-31G^* basis set was used in this calculation. In order to study all possible dissociation energies, some related species such as NLi₂Na, NLi _n (n = 1–4), Li _n (n = 1, 2) and Na _n (n = 1, 2) were also considered. Optimizations of these species were followed by fundamental frequency calculations at the same level. Global minima of these species were shown to adopt C _{2 v} (NLi₄Na₂, NLi₂Na₂), D _{3 h} (NLi₃Na₂) and C _s (NLiNa₂ and NLi₂Na) configurations. All possible dissociation energies were obtained. Received: 30 November 1998 / Accepted: 15 October 1999 / Published online: 14 March 2000     

Reactivity of C<Subscript>3</Subscript>-C<Subscript>8</Subscript> alkanes with nitronium ions in sulfuric acid

We have determined the parameters of the Arrhenius equation (E, log A) for reactions between \textNO₂⁺ {\text{NO}}_2^{+} ions and C₃-C₈ alkanes in HNO₃–93 wt.% H₂SO₄ solutions at 277–353 K, and we have also estimated the activation parameters E _j , log A _j for secondary and tertiary C—H bonds of these alkanes. We show that the following compensation relations are satisfied: E = 2.3R βlog A + C with isokinetic temperature β = 360 ± 65 K, and also E _j =2.3Rβ _j log A _j  + C _j , for secondary C—H bonds, β₂ =300 ± 60, and for tertiary C—H bonds, β₃ =310 ± 50.     

Enhancement of Lovastatin Production by Supplementing Polyketide Antibiotics to the Submerged Culture of <Emphasis Type="Italic">Aspergillus terreus</Emphasis>

Feedback inhibition existed in lovastatin biosynthesis from Aspergillus terreus. Exogenous lovastatin and other different polyketide antibiotics biosynthesized by polyketide synthase were supplemented to the cultures of A. terreus to investigate their influences on lovastatin production. Supplementing exogenous lovastatin of 100 mg l⁻¹ at the early stage of fermentation and the fast stage of its biosynthesis resulted in decreases of 76.4% and 20% in final lovastatin production, respectively. However, the fungal cell growth was not affected; the growing cycle was only prolonged in the submerged cultivation. Separate supplementation of the five kinds of polyketide antibiotics such as tylosin, erythromycin, tetracycline, daunorobin, and rifamycin to the cultures resulted in increases of about 20~25% in the final lovastatin production. Especially, supplementing tylosin of 50 mg l⁻¹ at the beginning of lovastatin biosynthesis led to the final lovastatin production of 952.7 ± 24.3 mg l⁻¹, which was improved by 42% and 22% compared with that produced in the control and the original culture, respectively. These results are helpful to understand the regulations on lovastatin biosynthesis and improve the final desired metabolite contents in many antibiotics production.     

Production of Lipids Containing High Levels of Docosahexaenoic Acid by a Newly Isolated Microalga, <Emphasis Type="Italic">Aurantiochytrium</Emphasis> sp. KRS101

In the present study, a novel oleaginous Thraustochytrid containing a high content of docosahexaenoic acid (DHA) was isolated from a mangrove ecosystem in Malaysia. The strain identified as an Aurantiochytrium sp. by 18S rRNA sequencing and named KRS101 used various carbon and nitrogen sources, indicating metabolic versatility. Optimal culture conditions, thus maximizing cell growth, and high levels of lipid and DHA production, were attained using glucose (60 g l⁻¹) as carbon source, corn steep solid (10 g l⁻¹) as nitrogen source, and sea salt (15 g l⁻¹). The highest biomass, lipid, and DHA production of KRS101 upon fed-batch fermentation were 50.2 g l⁻¹ (16.7 g l⁻¹ day⁻¹), 21.8 g l⁻¹ (44% DCW), and 8.8 g l⁻¹ (40% TFA), respectively. Similar values were obtained when a cheap substrate like molasses, rather than glucose, was used as the carbon source (DCW of 52.44 g l⁻¹, lipid and DHA levels of 20.2 and 8.83 g l⁻¹, respectively), indicating that production of microbial oils containing high levels of DHA can be produced economically when the novel strain is used.     

Platinum nanoparticle size effect on specific catalytic activity in <Emphasis Type="Italic">n</Emphasis>-alkane deep oxidation: Dependence on the chain length of the paraffin

The specific activity of 0.8% Pt/Al₂O₃ catalysts in the deep oxidation of C₁–C₆ n-alkanes increases with an increase in the Pt particle size from 1 to 3–4 nm. Further coarsening of the particles insignificantly changes the specific activity. The size effect was studied for a series of catalysts containing platinum nanoparticles 1 to 11 nm in diameter. The specific catalytic activity variation range depends on the size of the reacting hydrocarbon molecules. As the platinum particle size increases, the specific catalytic activity increases 3–4 times for the oxidation of CH₄ and C₂H₆ and by a factor of 20–30 for the oxidation of n-C₄H₁₀ and n-C₆H₁₄.     

Theoretical Study of the Interactions between Isolated <Emphasis Type="Italic">DNA</Emphasis> Bases and Various Groups IA and IIA Metal Ions by <Emphasis Type="Italic">Ab Initio</Emphasis> Calculations

Summary. Interactions of the DNA bases adenine (A), guanine (G), cytosine (C), and thymine (T) with various metal ions (M) of groups IA and IIA of the periodic table of the elements were studied at the HF, MP2, and DFT levels of theory. The structures and thermodynamic stabilities of these species were studied at the gas phase. The calculations uphold that there exist two active sites in G and one in A, C, and T. The calculations also show that the O² atom in T is a more active site for metal ion bindings than that in C. The stability energies for G … M complexes are larger than those for A … M complexes and the stability energies for T … M complexes are larger than those for C … M complexes. As z/r ratio for the metal ion increases, the interaction energy for the complex increases systematically. Thermodynamic quantities such as ΔH, ΔG, ΔS, and ln K were determined for each complexation reaction, [Base+M ⁿ⁺ →(Base … M) ⁿ⁺]. A, G, and C complexation reactions except for C … Rb⁺ are exothermic. The situation is quite different for T complexation reactions and all except for T … Be²⁺ and T … Mg²⁺ are endothermic.     

Biomolecular profiling of metastatic prostate cancer cells in bone marrow tissue using FTIR microspectroscopy: a pilot study

Prostate cancer (CaP) cells preferentially metastasise to the bone marrow, a microenvironment that plays a substantial role in the sustenance and progression of the CaP tumour. Here we use a combination of FTIR microspectroscopy and histological stains to increase molecular specificity and probe the biochemistry of metastatic CaP cells in bone marrow tissue derived from a limited source of paraffin-embedded biopsies of different patients. This provides distinction between the following dominant metabolic processes driving the proliferation of the metastatic cells in each of these biopsies: glycerophospholipid synthesis from triacylglyceride, available from surrounding adipocytes, in specimen 1, through significantly high (p ≤ 0.05) carbohydrate (8.23 ± 1.44 cm⁻¹), phosphate (6.13 ± 1.5 cm⁻¹) and lipid hydrocarbon (24.14 ± 5.9 cm⁻¹) signals compared with the organ-confined CaP control (OC CaP), together with vacuolation of cell cytoplasm; glycolipid synthesis in specimen 2, through significantly high (p ≤ 0.05) carbohydrate (5.51 ± 0.04 cm⁻¹) and high lipid hydrocarbon (17.91 ± 2.3 cm⁻¹) compared with OC CaP, together with positive diastase-digested periodic acid Schiff staining in the majority of metastatic CaP cells; glycolysis in specimen 3, though significantly high (p ≤ 0.05) carbohydrate (8.86 ± 1.78 cm⁻¹) and significantly lower (p ≤ 0.05) lipid hydrocarbon (11.67 ± 0.4 cm⁻¹) than OC CaP, together with negative diastase-digested periodic acid Schiff staining in the majority of metastatic CaP cells. Detailed understanding of the biochemistry underpinning the proliferation of tumour cells at metastatic sites may help towards refining chemotherapeutic treatment.     

Mechanisms for the formation of layered A<Subscript>4</Subscript>B<Subscript>3</Subscript>O<Subscript>12</Subscript> compounds from coprecipitated hydroxocarbonate and hydroxide systems

We have established and analyzed the sequences of phase transitions in synthesis of layered compounds in the A_nB_n–1O_3n family ( \textA₃^\textII\textLnB₃^\textV\textO₁₂ {\text{A}}_3^{\text{II}}{\text{LnB}}_3^{\text{V}}{{\text{O}}_{{12}}} (A^II = Ba, Sr, Ln = La, Nd, B^V = Nb, Ta) and La₄Ti₃O₁₂ with n = 4) from coprecipitated hydroxocarbonate and hydroxide systems, including steps involving the formation, solid-phase reaction, or structural rearrangement of intermediates.     

Self-association of n -hexyltrimethyl-ammonium bromide in aqueous electrolyte solution

 The self-association of n-hexyltrimethylammonium bromide (C₆TAB) in aqueous solution has been studied by static and dynamic light scattering and NMR spectroscopy at 25 °C in the presence of added electrolyte, and critical aggregation concentrations, aggregation numbers and the degree of ionization have been calculated. Aggregation numbers determined from light scattering and from the application of mass-action theory to the concentration dependence of ¹H NMR chemical shifts of four protons along the alkyl chain of C₆TAB, were between three and four over the range of electrolyte concentration studied (0.2–0.7  molkg⁻¹ NaBr). A structure for the small aggregates has been proposed from the NMR chemical shift data. Received: 4 June 2001 Accepted: 17 September 2001     

<Emphasis Type="Italic">Ab initio</Emphasis> Study of Structural and Conformational Properties of Five- to Nine-Membered Cyclic 1,2,3-Trienes

Summary.  The structures and relative energies of fundamental conformations of cyclopenta-1,2,3-triene, cyclohexa-1,2,3-triene, cylohepta-1,2,3-triene, cycloocta-1,2,3-triene, and cyclonona-1,2,3-triene were calculated by the HF/6-31G^* and MP2/6-31G^*//HF/6-31G^* methods. Only a C _2v symmetric planar conformation is available to cyclopenta-1,2,3-triene and cyclohexa-1,2,3-triene. The calculated energy barrier for ring inversion of the C _S symmetric puckerd conformation of cyclohepta-1,2,3-triene via the planar geometry is 62.2 kJ·mol⁻¹. The C ₂ symmetric twist conformation of cycloocta-1,2,3-triene was calculated to be the most stable one. Conformational racemization of the twist form takes place via the C _S symmetric half-chair geometry, which is by 60.8 kJ·mol⁻¹ less stable than the twist conformer. The C _S symmetric chair and unsymmetrical twist-boat conformations of cyclonona-1,2,3-triene were calculated to have similar energies; their interconversion takes place via an unsymmetrical low-energy (18.4 kJ·mol⁻¹) transition state. The twist (C ₂) and boat (C _S) geometries of cyclonona-1,2,3-triene are higher in energy by 13.2 and 33.9 kJ·mol⁻¹, respectively. Ring inversion in chair and twist-boat conformations takes place via a twist form as intermediate and requires 33.6 kJ·mol⁻¹. Corresponding author. E-mail: isayavar@yahoo.com Received March 25, 2002; accepted April 4, 2002