Terminal Methoxy Group Research Articles

Influence of Molecular Structures of Organic Foulants on the Antifouling Properties of Poly(2-methoxyethyl acrylate) and Its Analogs: A Molecular Dynamics Study.

Elucidating the fouling phenomena of polymer surfaces will facilitate the molecular design of high-performance biomedical devices. Here, we investigated the remarkable antifouling properties of two acrylate materials, poly(2-methoxyethyl acrylate) (PMEA) and poly(3-methoxypropionic acid vinyl ester) (PMePVE), which have a terminal methoxy group on the side chain, via molecular dynamics simulations of binary mixtures of acrylate/methacrylate trimers with n-pentane or 2,2-dimethylpropane (neopentane), that serve as the nonpolar organic probe (organic foulants). The second virial coefficient (B2) was determined to assess the aggregation/dispersion properties in the binary mixtures. The order of the B2 values for the trimer/pentane mixtures indicated that the terminal methoxy group of the side chain plays an important role in enhancing the fouling resistance to nonpolar organic foulants. Here, we hypothesized that the antifouling properties of PMEA/PMePVE surfaces originate from the resistance. To evaluate the molecular-level accessibility of organic foulants to acrylate/methacrylate materials, we examined the radial distribution functions (RDFs) of the terminal methyl groups of neopentane around the main chains of the acrylate/methacrylate trimers. As a result, the third distinct RDF peaks are observed only for the methacrylate trimers. The peaks are attributed to the hydrophobic interactions between the methyl group of neopentane and that of the main chain of the trimer. Accordingly, the methyl group of the main chain of methacrylate materials, such as poly(2-hydroxyethyl methacrylate) and poly(2-methoxyethyl methacrylate), unfavorably induces fouling with organic foulants. In this study, we clarify that preventing hydrophobic interactions between an organic foulant and polymeric material is essential for enhancing the antifouling property. Our approach has great potential for evaluating the molecular-level affinities of organic foulant with polymer surfaces for the molecular design of excellent antifouling polymeric materials.

Construction of highly ductile, UV-shielding polylactide/poly(butylene adipate-co-terephthalate) biocomposites with hyperbranched polysiloxane functionalized lignin as a biocompatibilizer

Biodegradable polylactide/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends have been widely utilized as packaging materials. However, it is urgent to develop a biocompatibilizer to improve the interfacial interaction of the biodegradable immiscible polymer blends in practice. In this paper, a novel type of hyperbranched polysiloxane (HBPSi) with terminal methoxy groups was synthesized and then utilized to functionalize lignin through a hydrosilation reaction. The HBPSi modified lignin (lignin@HBPSi) was incorporated into immiscible PLA/PBAT blends to serve as a biocompatibilizer. The lignin@HBPSi was uniformly dispersed in the PLA/PBAT matrix with improved interfacial compatibility. Dynamic rheological results revealed that the addition of lignin@HBPSi reduced the complex viscosity, improving the processing ability of the PLA/PBAT composite. The PLA/PBAT composite containing 5 wt% lignin@HBPSi had a superior toughness with an elongation at break of 300.2 % and a slight enhancement in tensile stress (34.47 MPa). In addition, the presence of lignin@HBPSi contributed to blocking ultraviolet rays in the full ultraviolet band. This work provides a feasible way to develop highly ductile PLA/PBAT/lignin composites with good UV-shielding properties for the packaging applications.

Accelerated clearance by antibodies against methoxy PEG depends on pegylation architecture.

Methoxy polyethylene glycol (mPEG) is attached to many proteins, peptides, nucleic acids and nanomedicines to improve their biocompatibility. Antibodies that bind PEG are present in many individuals and can be generated upon administration of pegylated therapeutics. Anti-PEG antibodies that bind to the PEG "backbone" can accelerate drug clearance and detrimentally affect drug activity and safety, but no studies have examined how anti-methoxy PEG (mPEG) antibodies, which selectively bind the terminus of mPEG, affect pegylated drugs. Here, we investigated how defined IgG and IgM monoclonal antibodies specific to the PEG backbone (anti-PEG) or terminal methoxy group (anti-mPEG) affect pegylated liposomes or proteins with a single PEG chain, a single branched PEG chain, or multiple PEG chains. Large immune complexes can be formed between all pegylated compounds and anti-PEG antibodies but only pegylated liposomes formed large immune complexes with anti-mPEG antibodies. Both anti-PEG IgG and IgM antibodies accelerated the clearance of all pegylated compounds but anti-mPEG antibodies did not accelerate clearance of proteins with a single or branched PEG molecule. Pegylated liposomes were primarily taken up by Kupffer cells in the liver, but both anti-PEG and anti-mPEG antibodies directed uptake of a heavily pegylated protein to liver sinusoidal endothelial cells. Our results demonstrate that in contrast to anti-PEG antibodies, immune complex formation and drug clearance induced by anti-mPEG antibodies depends on pegylation architecture; compounds with a single or branched PEG molecule are unaffected by anti-mPEG antibodies but are increasingly affected as the number of PEG chain in a structure increases.

A Maleimide-Terminally Modified PEGylated Liposome Induced the Accelerated Blood Clearance Independent of the Production of Anti-PEG IgM Antibodies.

PEGylated liposomes (PL) lose their long-circulating characteristic when administered repeatedly, called the accelerated blood clearance (ABC) phenomenon. The ABC phenomenon is generally thought to occur when the anti-polyethylene glycol (PEG) antibody (anti-PEG immunoglobulin M (IgM)) expressed in the spleen B cells triggered by the first dose of PL binds to the second and subsequent doses of PL, leading to activation of the complement system. MAL-PEG-DSPE, a PEG lipid with a maleimide (MAL) group at the PEG terminal, is used in various studies as a linker for ligand-bound liposomes such as antibody-modified liposomes. However, most ABC phenomenon research used PL with a terminal methoxy group (PL-OCH3). In this study, we prepared MAL-PEG-DSPE liposomes (PL-MAL) to evaluate the effect of PL-MAL on the ABC phenomenon induction compared to PL-OCH3. Pharmacokinetic, anti-PEG IgM secretion and complement activation analyses of these liposomes were conducted in mice. Interestingly, despite C3 bound to the surface of the initially administered PL-MAL, the administered PL-MAL showed high blood retention, demonstrating the same results as PL-OCH3. On the other hand, although the secretion of anti-PEG IgM induced by PL-MAL was lower than PL-OCH3, the second dose of PL-MAL rapidly disappeared from the blood. These results suggest that the antibody produced from the first dose of PL-MAL binds to the second dose of PL-MAL, thereby activating C3 to act as an opsonin which promotes phagocytic uptake. In conclusion, PL-MAL induced the ABC phenomenon independent of the production of IgM antibodies against PEG. This study provides valuable findings for further studies using ligand-bound liposomes.

Structural determination of an antibody that specifically recognizes polyethylene glycol with a terminal methoxy group

Covalent attachment of methoxy poly(ethylene) glycol (mPEG) to therapeutic molecules is widely employed to improve their systemic circulation time and therapeutic efficacy. mPEG, however, can induce anti-PEG antibodies that negatively impact drug therapeutic effects. However, the underlying mechanism for specific binding of antibodies to mPEG remains unclear. Here, we determined the first co-crystal structure of the humanized 15-2b anti-mPEG antibody in complex with mPEG, which possesses a deep pocket in the antigen-binding site to accommodate the mPEG polymer. Structural and mutational analyses revealed that mPEG binds to h15-2b via Van der Waals and hydrogen bond interactions, whereas the methoxy group of mPEG is stabilized in a hydrophobic environment between the VH:VL interface. Replacement of the heavy chain hydrophobic V37 residue with a neutral polar serine or threonine residue offers additional hydrogen bond interactions with methoxyl and hydroxyl groups, resulting in cross-reactivity to mPEG and OH-PEG. Our findings provide insights into understanding mPEG-binding specificity and antigenicity of anti-mPEG antibodies.

Synthesis, mesomorphic properties, and theoretical study of benzothiazole-aromatic molecules with ester- and azomethine-linking groups

ABSTRACT Two novel groups of rod-like molecules with benzothiazole-aromatic systems: one group (group A) having an ester linkage with different thioalkyl chain length and the other (group B) ester- and azomethine-linkages with methoxy groups in the tip of the molecules were synthesised. The structures of the synthesised compounds were confirmed by using physicochemical techniques such as 1H NMR, mass spectra, FT-IR spectra, melting points, and elemental analyses. Differential scanning calorimeter and polarising optical microscopy have been employed to verify their liquid crystalline behaviours and transition temperatures. All the synthesised compounds (groups A and B) showed enantiotropic nematic phase except the compound 13d showed the nematic phase in cooling only. The mesomorphic properties of the present compounds were compared with some other structurally related compounds to understand the chemical structure–mesophase properties relationship. The thermal range of nematic phase for the compounds (group A) were decreased with the increase of the thioalkyl chain length. The liquid crystalline properties of the compounds (group B) were greatly affected by the position of terminal methoxy groups. The change of the position of terminal methoxy groups in the compounds (group B) was theoretically studied to investigate if the theoretical calculations possess an agreement with the practical results.

Effect of the Surface Properties of γ-Al2O3 on the Conversion of Methanol into Dimethyl Ether According to in situ IR-Spectroscopic Data

The samples of alumina of different origin exhibit different activity in the reaction of methanol dehydration to dimethyl ether (DME). To elucidate reasons for differences in their activity, a comparative study of the structural (XRD analysis, specific surface area, and porosity) and surface (Bronsted and Lewis acidity and hydroxyl coverage) properties of alumina samples was carried out. The presence of formates, aldehyde complexes, and bridging and terminal methoxy groups in different ratios on the surface of aluminum oxide samples under the reaction conditions of methanol conversion was detected using in situ IR spectroscopy. The reactivity of the detected surface compounds was compared for all of the samples. It was found that the activity of the samples in the formation of DME correlated with the rate of conversion of bridging methoxy groups. In turn, the rate of conversion of the bridging methoxy groups was determined by the acidity of bridging hydroxyl groups. An increase in acidity led to an increase in the bond strength of the methoxy group with the surface and a decrease in the rate of its conversion into DME. Linear methoxy groups underwent oxidative conversion into formate and aldehyde surface complexes. The nature of the oxidizing ability of an alumina surface is discussed.

The tautomerization and ring closure in the Claisen rearrangement: A DFT study

AbstractElementary processes of the aromatic Claisen rearrangement were investigated by DFT calculations. First, rearrangements of four substrates Ph—O—CH2—CHCH2 [A], Ph—O—CH2—CHCH(OMe) [B], Ph—O—CH2—CHCH2····BF3 [C], and Ph—O—CH—CHCH(OMe)····BF3 [D] were examined. In these systems, the tautomerization is initiated by the intermolecular proton transfer involving the transient ion‐pair intermediate. An ignition‐propagation chain‐reaction mechanism in the tautomerization was suggested. For [A], the (ortho‐allyl phenol → α‐methyl‐dihydrobenzofuran (α‐methyl‐cumarane)) process was found to be ready and the product of the Claisen rearrangement seems to be the cumarane rather than the phenol. In [D] (activated both by the terminal methoxy group and by the BF3 catalyst), not the [3,3]‐sigmatropic shift but the tautomerization is the rate determining step. Second, the parent system, Ph—O—CH2—CHCH2, was investigated with (H2O) n (n = 2, 4, 6, and 10) systematically. The tautomerization takes place by the proton transfer via the water dimer or trimer. Except n = 2, similar changes of Gibbs free energies were obtained from the ether substrate to the cumarane.

Robust Red Organic Nanoparticles for In Vivo Fluorescence Imaging of Cancer Cell Progression in Xenografted Zebrafish

Bright and red‐emissive organic nanoparticles (NPs) are demonstrated as promising for in vivo fluorescence imaging. However, most red organic dyes show greatly weakened or quenched emission in the aggregated state. In this work, a robust red fluorophore (t‐BPITBT‐TPE) with strong aggregate‐state photoluminescence and good biocompatibility is presented. The NPs comprised of t‐BPITBT‐TPE aggregates encapsulated within 1,2‐distearoyl‐sn‐glycero‐3‐phosphoethanolamine‐N‐[methoxy(polyethylene glycol) (DSPE‐mPEG) micelles exhibit a photoluminescence peak at 660 nm with a high fluorescence quantum yield of 32% in aqueous media. The NPs can be facilely charged by using the same polymeric matrix with different terminal groups, e.g., methoxy (DSPE‐mPEG), amine (DSPE‐PEG‐NH2), or carboxymethyl (DSPE‐PEG‐COOH) groups. The biocompatibility, toxicity, circulation, and biodistribution of the NPs are assessed using the zebrafish model through whole embryo soaking and intravenous delivery. Furthermore, HeLa and MCF‐7 cells tagged with t‐BPITBT‐TPE in DSPE‐PEG‐NH2‐TAT polymer NPs are xenografted into zebrafish larvae to successfully track the cancer cell proliferation and metastasis, demonstrating that these new NPs are efficient cancer cell trackers. In addition, the NPs also show good in vivo imaging ability toward 4T1 tumors in xenografted BALB/c mice.

Chiro-optic and nonlinear optical studies of bridged triarylamine heterohelicenes; A DFT study

Density Functional Theory at B3PW91/6-311G (d, p) level was employed to analyze the spectral properties and nonlinear optical response of the oxo and thia-bridged triarylamine heterohelicenes. The energy calculations of optimized geometries reveals that the M and P isomeric forms of heterohelicenes of 1, 2, 3 and 4 are enantiomers, while as for 5, 6 and 7 they are atropisomers. The simulated Infrared and Vibrational circular dichroism spectra in the mid-infrared region (1300-1650 cm−1) display peaks, having contribution from out-of-phase stretching of the three fused aromatic rings and contribution from the three NC bond stretching. In addition to these peaks M-7 displays peak corresponds to bending of HCH of terminal methoxy group. In this study we have observed the oxo-bridged heterohelicenes displays higher values of hyperpolarizability as compared to thia-bridged heterohelicenes. In case of M-5, M-6 and M-7 the calculation reveals that with increase in electron donating capacity of substituent the hyperpolarizability increase due to decrease in optical band gap. Therefore, the oxo- and thia-bridged heterohelicenes can act as good raw material for nonlinear optical device and their nonlinear optical response can be enhanced by the extension in π-conjugation or addition of electron donating substituents.

Selective functional activity measurement of a PEGylated protein with a modification-dependent activity assay

BAX 855 (ADYNOVATE) is a PEGylated recombinant factor VIII (rFVIII) that showed prolonged circulatory half-life compared to unmodified rFVIII in hemophilic patients. Here, the development and validation of a novel assay is described that selectively measures the activity of BAX 855 as cofactor for the serine protease factor IX, which actives factor X. This method type, termed modification-dependent activity assay, is based on PEG-specific capture of BAX 855 by an anti-PEG IgG preparation, followed by a chromogenic FVIII activity assay. The assay principle enabled sensitive measurement of the FVIII cofactor activity of BAX 855 down to the pM-range without interference by non-PEGylated FVIII. The selectivity of the capture step, shown by competition studies to primarily target the terminal methoxy group of PEG, also allowed assessment of the intactness of the attached PEG chains. Altogether, the modification-dependent activity not only enriches, but complements the group of methods to selectively, accurately, and precisely measure a PEGylated drug in complex biological matrices. In contrast to all other methods described so far, it allows measurement of the biological activity of the PEGylated protein. Data obtained demonstrate that this new method principle can be extended to protein modifications other than PEGylation and to a variety of functional activity assays.

The Mystery of Antibodies Against Polyethylene Glycol (PEG) - What do we Know?

Recent findings demonstrated anti-PEG antibody formation in some healthy individuals and patients who have not received PEGylated biotherapeutics. Some of these findings evoked criticism because of shortcomings in the antibody assays used. To better understand this topic, we established robust antibody analytics and screened two cohorts of healthy individuals and one cohort of hemophilia patients for the expression of anti-PEG antibodies. A flow cytometry approach and a fully validated ELISA platform were established to detect specific anti-PEG antibodies. Immunohistochemistry was used to test for potential binding of anti-PEG antibodies to human tissues. IgM and/or IgG anti-PEG antibodies are expressed by some healthy individuals and by some patients with hemophilia who have not received PEGylated biotherapeutics. These antibodies can be either transient or persistent and recognize PEGs of different sizes with or without terminal methoxy groups. Age and location of healthy individuals influence the prevalence of IgG but not of IgM antibodies. Anti-PEG antibodies do not cross-react with human tissues supporting the safety of the antibodies. We confirm that some healthy individuals and some patients with hemophilia express specific antibodies against PEG which are not associated with any pathology and do not bind to human tissues.

Effect of Ligand Substitution around the Dy(III) on the SMM Properties of Dual-Luminescent Zn-Dy and Zn-Dy-Zn Complexes with Large Anisotropy Energy Barriers: A Combined Theoretical and Experimental Magnetostructural Study.

The new dinuclear Zn(II)-Dy(III) and trinuclear Zn(II)-Dy(III)-Zn(II) complexes of formula [(LZnBrDy(ovan) (NO3)(H2O)](H2O)·0.5(MeOH) (1) and [(L(1)ZnBr)2Dy(MeOH)2](ClO4) (3) (L and L(1) are the dideprotonated forms of the N,N'-2,2-dimethylpropylenedi(3-methoxysalicylideneiminato and 2-{(E)-[(3-{[(2E,3E)-3-(hydroxyimino)butan-2-ylidene ]amino}-2,2-dimethylpropyl)imino]methyl}-6-methoxyphenol Schiff base compartmental ligands, respectively) have been prepared and magnetostructurally characterized. The X-ray structure of 1 indicates that the Dy(III) ion exhibits a DyO9 coordination sphere, which is made from four O atoms coming from the compartmental ligand (two methoxy terminal groups and two phenoxido bridging groups connecting Zn(II) and Dy(III) ions), other four atoms belonging to the chelating nitrato and ovanillin ligands, and the last one coming to the coordinated water molecule. The structure of 3 shows the central Dy(III) ion surrounded by two L(1)Zn units, so that the Dy(III) and Zn(II) ions are linked by phenoxido/oximato bridging groups. The Dy ion is eight-coordinated by the six O atoms afforded by two L(1) ligands and two O atoms coming from two methanol molecules. Alternating current (AC) dynamic magnetic measurements of 1, 3, and the previously reported dinuclear [LZnClDy(thd)2] (2) complex (where thd = 2,2,6,6-tetramethyl-3,5-heptanedionato ligand) indicate single molecule magnet (SMM) behavior for all these complexes with large thermal energy barriers for the reversal of the magnetization and butterfly-shaped hysteresis loops at 2 K. Ab initio calculations on 1-3 show a pure Ising ground state for all of them, which induces almost completely suppressed quantum tunnelling magnetization (QTM), and thermally assisted quantum tunnelling magnetization (TA-QTM) relaxations via the first excited Kramers doublet, leading to large energy barriers, thus supporting the observation of SMM behavior. The comparison between the experimental and theoretical magnetostructural data for 1-3 has allowed us to draw some conclusions about the influence of ligand substitution around the Dy(III) on the SMM properties. Finally, these SMMs exhibit metal- and ligand-centered dual emissions in the visible region, and, therefore, they can be considered as magnetoluminescent bifunctional molecular materials.

A theoretical study of benzaldehyde derivatives as tyrosinase inhibitors using Ab initio calculated NQCC parameters.

Tyrosinase is a multifunctional copper-containing enzyme. It can catalyze two distinct reactions of melanin synthesis and benzaldehyde derivatives, which are potential tyrosinase inhibitors. To find the relationships between charge distributions of benzaldehyde and their pharmaceutical behavior, the present study aimed at investigating nuclear quadrupole coupling constants of quadrupolare nuclei in the functional benzaldehyde group and calculating some its derivatives. In addition, the differences between the electronic structures of various derivatives of this depigmenting drug were examined. All ab initio calculations were carried out using Gaussian 03. The results predicted benzaldehyde derivatives to be bicentral inhibitors; nevertheless, the oxygen or hydrogen contents of the aldehyde group were not found to be the only active sites. Furthermore with the presence of the aldehyde group, the terminal methoxy group in C4 was found to contribute to tyrosinase inhibitory activities. In addition, an oxygen atom with high charge density in the side chain was found to play an important role in its inhibitory effect.

Synthesis and Antimicrobial Evaluation of 6-Alkylamino-N-phenylpyrazine-2-carboxamides.

This work presents synthesis and antimicrobial evaluation of nineteen 6-alkylamino-N-phenylpyrazine-2-carboxamides. Antimycobacterial activity was determined against Mycobacterium tuberculosis H37Rv, M.kansasii and two strains of M.avium. Generally, the antimycobacterial activity increased with prolongation of simple alkyl chain and culminated in compounds with heptylamino substitution (3e, 4e) with MIC=5-10μm against M.tuberculosis H37Rv. On the contrary, derivatives with modified alkyl chain (containing e.g. terminal methoxy or hydroxy group) as well as phenylalkylamino derivatives were mainly inactive. The most active compounds (with hexyl to octylamino substitution) were evaluated for their in vitro activity against drug-resistant strains of M.tuberculosis and possessed activity comparable to that of the reference drug isoniazid. None of the tested compounds were active against M.avium. Some derivatives exhibited activity against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (best MIC=7.8μm), while Gram-negative strains as well as tested fungal strains were completely unsusceptible. Active compounds were tested for in vitro toxicity on various cell lines and in most cases were non-toxic up to 100μm.

Synthesis and antimycobacterial evaluation of 5-alkylamino-N-phenylpyrazine-2-carboxamides

Substitution of chlorine in 5-chloro-N-phenylpyrazine-2-carboxamide (1) with simple n-alkylamines yielded a series of 5-alkylamino-N-phenylpyrazine-2-carboxamides (propylamino to octylamino derivatives), which possessed similar or increased activity against Mycobacterium tuberculosis H37Rv compared to parent 5-chloro derivative (1), with MIC ranging from 2.5 to 12.2μM. 5-Butylamino to 5-heptylamino derivatives exerted similar activity also against Mycobacterium kansasii. Importantly, the substitution led also to significant decrease of in vitro cytotoxicity in HepG2 cell line. 5-Heptylamino-N-phenylpyrazine-2-carboxamide (1e) exerted MIC=2.5μM (M.tbc) and IC50 >250μM (HepG2). Further modification of alkylamino chain with terminal methoxy or hydroxy group lead to compounds with decreased or none activity, the decrease was proportional to the decrease of lipophilicity. 5-(2-Phenylethylamino) and 5-(3-phenylpropylamino) derivatives were also of decreased activity. On contrary to alkylamino derivatives derived from 1, alkylamino derivatives derived from 5-chloro-N-2-chlorophenylpyrazine-2-carboxamide (2) possessed substantially decreased or none activity. None of the prepared compounds was active against Mycobacterium avium.

Acetal Derivatives as Prodrugs of Resveratrol

The pharmacological exploitation of resveratrol is hindered by rapid phase-II conjugative metabolism in enterocytes and hepatocytes. One approach to the solution of this problem relies on prodrugs. We report the synthesis and characterization as well as the assessment of in vivo absorption and metabolism of a set of prodrugs of resveratrol in which the OH groups are engaged in the formal (-OCH2OR) or the more labile acetal (-OCH(CH3)OR) linkages. As carrier group (R) of the prodrug, we have used short ethyleneglycol oligomers (OEG) capped by a terminal methoxy group: -O-(CH2CH2O)n-CH3 (n = 0, 1, 2, 3, 4, 6). These moieties are expected to exhibit, to a degree, the favorable properties of longer polyethyleneglycol (PEG) chains, while their relatively small size makes for a more favorable drug loading capacity. After administration of formal-based prodrugs to rats by oral gavage, significant concentrations of derivatives were measured in blood samples over several hours, in all cases except for n = 0. Absorption was maximal for n = 4. Complete deprotection to give resveratrol and its metabolites was however too slow to be of practical use. Administration of the acetal prodrug carrying tetrameric OEG chains resulted instead in the protracted presence of resveratrol metabolites in blood, consistent with a progressive regeneration of the parent molecule from the prodrug after its absorption. The results suggest that prodrugs of polyphenols based on the acetal bond and short ethyleneglycol oligomers of homogeneous size may be a convenient tool for the systemic delivery of the unconjugated parent compound.

Characterization of Low-Molecular Weight Iodine-Terminated Polyethylenes by Gas Chromatography/Mass Spectrometry and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry with the Use of Derivatization

Gas chromatography/mass spectrometry (GC/MS) and matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry, in conjunction with various derivatization approaches, have been applied to structure determination of individual oligomers and molecular-mass distributions (MMD) in low-molecular mass polyethylene having an iodine terminus. Direct GC/MS analysis has shown that the samples under investigation composed of polyethyelene-iodides (major components) and n-alkanes. Exchange reaction with methanol in the presence of NaOH gave rise to methoxy-derivatives and n-alkenes. Electron ionization mass spectra have shown that the former contained terminal methoxy groups indicating the terminal position of the iodine atom in the initial oligomers. MMD parameters have been determined with the aid of MALDI mass spectrometry followed by preliminary derivatization-formation of covalently bonded charge through the reaction of iodides with triphenylphosphine, trialkylamines, pyridine or quinoline. The mass spectra revealed well-resolved peaks for cationic parts of derivatized oligomers allowing the determination of MMD. The latter values have been compared with those calculated from GC/MS data.

Synthesis and applications of new triphenylamine dyes with donor–donor–(bridge)–acceptor structure for organic dye-sensitized solar cells

Four novel asymmetric triphenylamine dyes configured with donor–donor–acceptor (D–D–A) and donor–donor–bridge–acceptor (D–D–π–A) structures were synthesized and applied to organic dye-sensitized solar cells. The terminal methoxy group in the donor part and the furane-bridge unit contributed to the wider absorption region and enhanced electron life time, resulting in a higher photocurrent density (Jsc), open-circuit voltage (Voc), and overall conversion efficiency (η). Among the synthesized dyes, the SK2-based DSSC showed the highest conversion efficiency of 5.57% (Jsc = 10.41 mA cm−2, Voc = 729 mV, and FF = 0.73) caused by the synergetic effect of the methoxy group and the furane-bridge unit.

Improvement of Aminopeptidase Activity of Dizinc(II) Complexes by Increasing Substrate Accessibility

A new dizinc(II) complex, [Zn2(bhmp)(MeCO2)2]BPh4 [(bhmp)−: 2,6-bis[bis(2-hydroxyethyl)aminomethyl]-4-methylphenolate anion], performs aminopeptidase activity to hydrolyze L-leucine-p-nitroanilide. As compared with a related dizinc(II) complex [Zn2(bomp)(MeCO2)2]BPh4 [(bomp)−: 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-methylphenolate anion], the activity of the present bhmp complex was about 80 times greater than that of the bomp complex. This is mainly because the substrate accessibility was improved by changing the terminal methoxy groups to hydroxyl groups.