Alkyl Chain Substitution Research Articles

Dioxane enhanced immobilization of urease on alkyl modified nano-porous silica using reversible denaturation approach

Abstract Efficient immobilization of urease was achieved upon dioxane-induced unfolding/refolding strategy on alkyl modified porous silica with an average pore size of 66 nm. Structural exploration of the urease was carried out to find the optimum condition of solvent polarity which provides efficient adsorptive immobilization through emphasizing on dual approaches: creation of hydrophobic intermediates as molten globule like states and improved accessibility of substituted alkyl chains. The optimum percent volume of dioxane in phosphate buffer to fulfill such aim was achieved at 30% (v/v). Restoring of native-like secondary structure was observed using circular dichroism; moreover, improved exposure of hydrophobic surfaces of urease was confirmed using a set of UV-analysis, intrinsic fluorescence, and differential 8-anilino-1-naphthalene-sulfonate fluorescence spectroscopy, at 30% as an optimum concentration of dioxane. The yield of immobilization was doubled using reversible denaturation approach and storage stability of the immobilization product of urease was noticeably improved (half live of the multi-used immobilized urease was resulted to be 6.5 folds higher than the half live of the free enzyme). Moreover, 7–13.5 folds activation of the enzyme was resulted upon immobilization. Improved immobilization ensures the efficiency of this strategy, for applied approaches, along with providing further evidences for enhanced surface hydrophobicity of the multimeric urease at defined concentration of dioxane.

Sebacic and succinic acid derived plasticised PVC for the inhibition of biofouling in its initial stages

In this work, we report the use of plasticized poly vinylchloride (PVC) as a potential antifouling coating material. The materials contain a variety of sebacic and succinic acid-derived plasticisers providing a variation in molecular shape and structure; diethyl succinate (DESn), di-(2-ethylhexyl sebacate) (DEHS), dibutyl sebacate (DBS), and diethyl sebacate (DES). Each plasticiser from the sebacate group possessed the same basic C10H16O4 moiety with varied dialkyl terminated groups, affording a different range of homologous series plasticisers. This work investigates whether branching of the side substituted alkyl chains on each plasticiser molecule affects microorganism attachment and subsequent fouling. The plasticized polymers are spin coated to create thin films for testing. In order to determine the antifouling capacity of the materials, the polymer coatings underwent a series of analyses for biomass determination, glycocalyx production, and protein and carbohydrate adsorption. Topological and morphological characterization was performed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). After a 7 day laboratory biofouling study it was found that the plasticisers with increased alkyl branching, DESN, and DEHS revealed the greatest degree of prevention of microorganism colonization and attachment thus significantly reducing the initial formation of biofilms by up to 65% in some biofouling assays when compared to the uPVC blank.

Thermal treatment effects on N-alkyl perylene diimide thin-film transistors with different alkyl chain

The authors report that thermal treatment effect on various N,N′-dialkyl-3,4,9,10-perylene tetracarbxylic diimides [PTCDI-Cn, alkyl–dodecyl (n=12), butadecyl (n=14), octadecyl (n=18)] thin-film transistors (TFTs) depends on the substituted alkyl chain length. It is clearly demonstrated that there are two kinds of molecular movements during the thermal treatment on PTCDI films; molecular rearrangement in the same layer and molecular migration from the lower layer to the upper layer. The former is directly related to the grain growth and can be controllable by applying an external electric field. The latter is also related not only to the grain growth but also to the formation of cracks between grains. These two movements show opposite dependence on the alkyl chain length during the thermal treatment; the former is more active in longer alkyl chain, but the latter in shorter one. However, they also have opposite effect to TFT performance, and PTCDI films with longer alkyl chains have great advantage on TFT performance for the thermal treatment. Consequently, PTCDI-C18 TFTs show the highest electron mobility as large as 1.2 cm2/V s after the thermal treatment at 140 °C.

Appraisal of Through-Bond and Through-Space Substituent Effects via Molecular Electrostatic Potential Topography

Through-bond (TB) and through-space (TS) substituent effects in substituted alkyl, alkenyl, and alkynyl arenes are quantified separately using molecular electrostatic potential (MESP) topographical analysis. The deepest MESP point over the aromatic ring (V(min)) is considered as a probe for monitoring these effects for a variety of substituents. In the case of substituted alkyl chains, the TS effect (79.6%) clearly dominates the TB effect, whereas in the unsaturated analogues the TB effect (∼55%) overrides the TS effect.

Tribological Performance of Ionic Liquids Bearing Hydroxyl Groups as Lubricants in the Aluminum-on-Steel Contacts

A series of room temperature ionic liquids bearing hydroxyl groups, namely 1-(3’-hydroxyl-n-propyl)-3-alkylimidazolium tetrafluoroborate or hexafluorophosphate, were prepared and characterized. Their typical physical properties were also determined. The tribological test results show that these ionic liquids possess better friction-reducing and anti-wear ability for aluminum-on-steel system than lubricant X-1P. The friction coefficients of them are little higher than that of the nonfunctionlized ionic liquid LP308, while they possess better anti-wear abilities than the latter, which may ascribe to the chemical activity of hydroxyl group. Both the anions and the side substituted alkyl chains attached to the imidazolium cations affect the tribological performance of the lubricants. The SEM, EDS and XPS analysis of the worn surfaces show that complicated tribo-chemical reactions were involved in the sliding process. The boundary films composed of fluorides, nitrogen oxide, BN, and FePO4 were generated on the rubbing aluminum surfaces, which contribute to effectively decreasing the friction and wear of the contacts.

Synthesis and characterization of low-toxic amphiphilic chitosan derivatives and their application as micelle carrier for antitumor drug

A new series of amphiphilically modified chitosan molecules with long alkyl chains as hydrophobic moieties and glycol groups as hydrophilic moieties (N-octyl-O-glycol chitosan, OGC) was synthesized for use as drug carriers. The chemical structure was characterized by Fourier transform infrared, 1H nuclear magnetic resonance, and elemental analysis. OGC could easily self-assemble to form nanomicelles in an aqueous environment and exhibited a low critical micellar concentration of 5.3–32.5 mg/L. The biocompatibility and low toxicity of OGC as excipient for the dosage forms aimed at i.v. administration were confirmed by hemolysis, acute toxicity and histopathological studies. Furthermore, the possibility of solubilizing paclitaxel (PTX), a water-insoluble antitumor drug, with OGC micelles was also explored. PTX was successfully loaded into OGC micelles by using a simple dialysis process. The drug-loading capacity of OGC and stability of drug-loaded micelles were significantly affected by the degree of substitution of alkyl chains. Moreover, a series of safety studies including hemolysis, hypersensitivity, maximum tolerated dose, acute toxicity, and organ toxicity revealed that the PTX-loaded OGC micelles had advantages over the commercially available injectable preparation of PTX (Taxol ®), in terms of low toxicity levels and increased tolerated dose. Additionally, cytotoxicity studies showed that the PTX-loaded OGC micelles were comparable to the commercial formulation, but the blank micelles were far less toxic than the Cremophor EL vehicle. These results suggest that OGC is a promising carrier for injectable PTX micelles.

Self-Assembly, Dynamics, and Phase Transformation Kinetics of Donor−Acceptor Substituted Perylene Derivatives

The role of alkyl chain substitution on the phase formation and core dynamics is studied in a series of diphenylamine functionalized perylenemonoimides (PMIs), by X-ray scattering, calorimetry and site-specific solid-state NMR techniques. In addition, the strong dipole associated with the donor-acceptor character of the molecules allow an investigation of the dynamics with dielectric spectroscopy. The self-assembly revealed an ordered phase only in PMIs with branched alkyl chains. This phase comprises a helical stacking of molecules with a molecular twist angle of 60 degrees. Results from solid-state NMR further pointed out the importance of intramolecular hydrogen bonding in stabilizing the intracolumnar packing within the ordered phase. Moreover, the core dynamics are frozen as revealed by the value of the dynamic order parameters and the reduced strength of dipolar relaxation. The kinetics of phase transformation from the isotropic to the ordered phase proceeds via a nucleation and growth mechanism, and the rates are dominated by the nucleation barrier. Within the isotropic phase the core dynamics display strong temperature dependence with rates that depend on the number of methylene units in the alkyl chains.

Synthesis and NMR assignment of pentacycloundecane precursors of potential pharmaceutical agents

The synthesis and complete NMR elucidation of eight novel pentacycloundecane (PCU) derivatives are reported. These compounds are precursors in the synthesis of PCU-based anti-tuberculosis (TB) agents and potential human immunodeficiency virus (HIV) protease inhibitors. Two-dimensional (2D) NMR techniques were used to assign the NMR spectra for these compounds. Substitution of the cage molecule at (C-8/11) further complicates the assignment, since some of the substituted alkyl chain groups overlap with the cage proton signals. The side chain heteroatoms also introduce a rare through-space deshielding effect to some of the carbon atoms of the cage skeleton. Ring strain in the rigid cage skeleton appears to induce drastic electronic changes in some parts of the cage framework. This observation is more dramatic for the C-4 methylene group of the cage diols and the cage ethers.

Processable donor–acceptor type electrochromes switching between multicolored and highly transmissive states towards single component RGB-based display devices

Donor–acceptor (DA) type polymers, poly(2-alkyl-4-(thiophen-2-yl)-2H-benzo[1,2,3]triazole)s (PTBT-DAs), with alternating alkyl chain substitution were synthesized and characterized in terms of their electrochemical and optical properties. Spray processable polymers have multicolored states upon oxidation and showed ambipolar characteristics in which n-type doping allowed them to achieve a transparent state in a low working potential range. Reported electrochemical and spectral results showed that PTBT-DAs are great candidates for single component electrochromic display devices. In the context of low cost flexible display device technology, requirements for polymers showing multicolored and transmissive states can be fulfilled by PTBT-DAs.

Toward strain resistant flexible organic thin film transistors

We suggest a molecular design for small molecules as polycrystalline organic semiconductors in flexible organic thin film transistor applications, providing an improved stability during substrate bending. A stable operation of alkyl-substituted sexithiophens was obtained under strain up to ±2.5%. The stability relates to the flexibility of the alkyl chain substitution, scales with their chain length, and outperforms those of pentacene devices. These findings were independent from the underlying dielectric layer.

Crystal structures of three host–guest complexes of methylsubstituted cucurbit[6]urils and anthracene derivatives

Three host–guest complexes of methylsubstituted cucurbit[6]urils host and anthracene derivatives guests were synthesized and structurally characterized by single crystal X-ray diffractions and 1H NMR technique. The hosts are dodecamethylcucurbit[6]uril (DDMeQ[6]), α,α′,δ,δ′-tetramethylcucurbit[6]uril (TMeQ[6]), and hexa-methylsubstituted cucurbituril (HSMeQ[6]) made from 3a-methyl-glycoluril. The guests are 9,10-bis[ N-(aminoethylene)aminomethyl]anthracene (AN1), 9,10-bis[ N-(aminopropylene) aminomethyl]anthracene (AN2) and 9,10-bis[ N-(aminobutylene)aminomethyl]anthracene (AN3). The crystal structures show the compounds 1–3 with stoichiometry of {DDMeQ[6]-AN1} 2+2NO 3 −24H 2O ( 1), {TMeQ[6]-AN2} 2+4NO 3 − 2H 3O +10H 2O ( 2) and {2HSMeQ[6]-AN3} 2+2Cl −25H 2O ( 3) respectively, and the formation of an exclusion or inclusion host–guest complex is dependent on the length of the substituted alkyl chains on the anthracene.

Effect of Electrostatic Interactions on Metallophthalocyanine Single Molecular Arrays with <I>n</I>-Octadecyl Mercaptan Templates

By changing central metal ions or by tuning the length of substituted alkyl chains, metallophthalocyanines or their derivatives exhibit various assembling behaviors when co-adsorbed with n-octadecyl mercaptan on highly oriented pyrolytic graphite surfaces. Repeated scanning tunneling microscopy experiments demonstrate that planar or short alkyl chain substituted MPcs could form single molecular arrays while phase separation occurred when non-planar or longer alkyl chain substituted MPcs were co-adsorbed with C18SH templates. The experimental results combined with the density functional theory calculations reveal that intermolecular electrostatic and van der Waals interactions play essential roles in the formation of single molecular arrays.

Novel cationic and amphiphilic pullulan derivatives I: Synthesis and characterization

Cationic amphiphilic modified pullulan’s were obtained in two steps: firstly the synthesis of diethylaminoethylpullulan (DEAE-Pullulan) with DS 0 = 0.80 in water (all degrees of substitution (DS) are calculated in anhydroglucose units (AGU)) followed by the incorporation of different alkyl chains (C 10, C 12 and C 16) using Hoffmann alkylation reaction. Three alkylated derivatives (Y-Cx-DEAE-Pullulan) were produced with a degree of substitution of alkyl chains (Y = 100 DS Cx) of 40 in the case of C10 and C12 and 20 in the case of C16. The three samples contained two functional types: an amine function (DS N), dependent on pH and a quaternary ammonium function (DS N+) linked to a hydrophobic alkyl chain (DS Cx). Chemical characterizations were carried out by conductimetric measurements, elemental analysis and 1H NMR. The amphiphilic and associative properties have been confirmed by flow field flow fractionation (F4) coupled on-line with multi-angle laser light scattering (MALLS). The intermolecular associations were observed for DEAE-Pullulan and Y-Cx-DEAE-Pullulan in 0.1 M LiNO 3.

Synthesis of high-luminescent cadmium sulfide nanocrystallites by a novel single-source precursor route

Highly luminescent cadmium sulfide nanocrystallites have been successfully produced by the thermolysis of a novel single-source precursor, cadmium O, O′-dialkyldithiophosphates, which were dissolved in oleic amine. The microstructure and morphology of the as-prepared CdS nanoparticles were characterized using X-ray diffraction, transmission electron microscopy and high resolution transmission electron microscopy. It was found that the as-prepared CdS nanoparticles show a narrow size distribution and high crystallinity. The optical properties of these samples were examined by UV–visible and photoluminescence spectroscopy. Not only an intensive red-light-emitting luminescence phenomenon derived from the solution of the CdS nanocrystallites can be observed easily at room temperature, the band gap of CdS nanocrystallites can also be tailored by changing the length of substituted alkyl chain of single-source precursors.

Synthesis, aggregation and photoconductive properties of alkoxycarbonyl substituted perylenes

A series of 3,4,9,10-tetra-( n-alkoxy-carbonyl)-perylene (PTAC, n = 4, 6, 8, 10, 12) derivatives with various alkyl chains were synthesized via a simple and efficient phase-transfer catalysis method. It was found that the length of the alkyl chains attached to the perylene skeleton greatly influenced aggregation behaviour. The finding that it was easier for PTAC derivatives with shorter alkyl chains to form crystal films was interpreted in terms of molecular volume and steric repulsion. The photoconductivity of the materials was investigated by xerographic photoinduced discharge technique and the results showed that photosensitivity increased with the decreasing length of the alkyl chain attached to perylene core. This result was consistent with the changing trend of aggregate structure observed for the PTAC derivatives used in this study: the shorter the substituted alkyl chain, the more ordered the film was and, thus, the greater was the photosensitivity.

Self-Organized Monolayer Formation from Binary Mixtures of Substituted Alkyl Chains Studied by STM

The molecular assembly of p-iodo-phenyl octadecyl ether (I-POE), p-iodo-phenyl docosyl ether (I-PDE) and a binary mixture of these two molecules on graphite has been studied using a scanning tunneling microscope. Each molecular system self-assembles on the graphite surface to form a stable monolayer. For the binary system, the I-POE and I-PDE molecules do not mix on the surface, preferring instead to form isolated monolayer domains. Here, the I-POE molecules are preferentially adsorbed on the graphite surface, due to the effects of alkyl chain length and the functional group on the monolayer structure.

Tuning the arrangement of mono-crown ether-substituted phthalocyanines in Langmuir–Blodgett films by the length of alkyl chains and the cation in subphase

Amphiphilic phthalocyanines with one crown ether and three alkyl chain substitutions can form stable monolayers on a water surface. This monolayer can be transferred to a substrate by a vertical dipping method. The arrangement of phthalocyanine molecules in LB films was affected by the length of alkyl chains and the coordination of alkali ions in crown ether. Davydov splitting was observed in the absorption spectra of the LB films of phthalocyanine with the shortest alkyl chain substitutions, and this splitting was affected by the alkali ions in the subphase.

Surface and Aggregation Behavior of Aqueous Solutions of Ru(II) Metallosurfactants. 3. Effect of Chain Number and Orientation on the Structure of Adsorbed Films of [Ru(bipy)2(bipy‘)]Cl2 Complexes

The surface behavior of a range of surfactant [Ru(bipy)(2)(p,p'-dialkyl-2,2'-bipy)]Cl(2) complexes, which we express as Ru(q)(p)C(n) where n is the alkyl chain length, p refers to the substitution position on the bipyridine ligand (=4 or 5), and q (=1 or 2) is the number of substituted alkyl chains, has been examined using neutron reflectometry. The adsorption of the single-chain Ru(1)(4)C(19) and Ru(1)(5)C(19) surfactants is strongly time-dependent, taking in excess of 10 h to form an equilibrium film. It is suggested that the slow adsorption rate is related to the alkyl chain length rather than the low monomer concentration present in the solutions. At concentrations below the critical micelle concentration (cmc) of Ru(1)(4)C(19), the film of Ru(1)(5)C(19) is denser than that of Ru(1)(4)C(19) at comparable concentration, consistent with the mass densities of the bulk solids, whereas at concentrations close to and greater than this cmc the converse pertains. Close to the cmc, the adsorbed films possess an average area per molecule significantly less than the nominal headgroup area of the surfactants (approximately 30 angstroms(2) compared with approximately 100 angstroms(2)). This fact together with consideration of the thickness and density of the adsorbed films leads to the conjecture that surface aggregates may be the adsorbing units. The adsorption of the double-chain surfactant Ru(1)(p)C(19), in contrast to the behavior of the Ru(1)(p)C(19) surfactants, is weak and independent of time. This behavior is attributed to the alkyl chain orientation. The adsorption behavior of a racemic mixture of the Delta and Lambda isomers of Ru(2)(4)C(19) has been compared with that of the Delta isomer. It is found that the film of racemic material is more closely packed than that of the resolved complex.

Two-Dimensional Supramolecular Assemblies of Quinacridone Derivatives: From Achiral to Chiral Racemates and Domains

We described the two-dimensional (2D) assemblies of N,N‘-dialkyl-substituted quinacridone derivatives on highly orientated pyrolytic graphite (HOPG) observed by scanning tunneling microscopy (STM), and focused on how minor structural variations can influence the supramolecular organization of the compounds. For quinacridone derivatives with or without methyl groups only the same enantiotopic faces of the quinacridone cores are observed with high resolution depending on the length of the substituted alkyl chains. For coadsorptions of quinacridone derivatives and fatty acids at the liquid/graphite interface, we have found interestingly that quinacridone derivatives with methyl groups form chiral racemates, whereas the quinacridone derivative without methyl groups forms chiral domains. The chiral 2D structures formed at the interface are only observed when fatty acids are present as guest molecules and for quinacridone derivatives substituted with long alkyl chains, −C22H45. These findings suggest that the 2D nanopatterned structure of quinacridone derivatives with light-emitting properties can be adjusted by controlling intermolecular interaction through tailor-made molecular building blocks and coadsorption.

Structure Features and Phase Behavior of 1-(12-Hydroxy)stearoyl-rac-glycerol Monolayers

The effect of the alkyl-chain substitution on ordering and phase behavior of monoglycerol esters is studied by coupling the results of surface pressure−area (π−A) isotherm measurements, Brewster angle microscopy, and grazing incidence X-ray diffraction. In the present work, structure features and phase behavior of 1-(12-hydroxy)stearoyl-rac-glycerol monolayers are investigated and compared with those of the nonsubstituted 1-stearoyl-rac-glycerol and 12-hydroxystearic acid monolayers. The dominating effect of the alkyl-chain substitution by a hydroxyl group in the 12 position on the monolayer properties is demonstrated. Phase behavior, domain morphology, and two-dimensional lattice structure of the two 12OH-substituted amphiphiles are similar to each other but different from those of the usual nonsubstituted amphiphiles. Main characteristics of the 1-(12-hydroxy)stearoyl-rac-glycerol monolayers are an extended flat phase-transition (plateau) region of the π−A isotherms related with a small temperature depe...