Molecular architecture of poly[(R,S)-3-hydroxybutyrate-co-6-hydroxyhexanoate] and poly[(R,S)-3-hydroxybutyrate-co-(R,S)-2-hydroxyhexanoate] oligomers investigated by electrospray ionization ion-trap multistage mass spectrometry

A series of aliphatic copolyesters was obtained from (R,S)-beta-butyrolactone and two isomeric hydroxy acids, 6-hydroxyhexanoic and (R,S)-2-hydroxyhexanoic acids. The reactions were conducted in bulk without catalyst. Electrospray ionization tandem mass spectrometry (ESI-MSn) was used for molecular characterization of these copolyester oligomers. The mass spectra of the copolyesters studied have enabled identification of their molecular structures including chemical nature of the end groups (hydroxyl and carboxylate). The compositions of the oligocopolyesters and their sequence distributions were determined based on measurement of the relative intensities of the individual oligocopolyester peaks in the ESI mass spectra. The mass spectra (MS1) provided information on composition and sequence distribution, and small deviations from Bernoulli statistics were detected. The arrangement of co-monomer structural units along the oligopolyester chains was verified by MS/MS experiments and investigation of the fragmentation pathways.     

Dielectric spectroscopy of biodegradable poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) films

In this paper, we report a systematic study of the dielectric relaxation spectroscopy of biodegradable poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) polyester which has potential applications as a “green” dielectric material in electronic devices. The dielectric spectra was measured over a wide frequency range (10⁰ ～ 10⁷ Hz) from ?100 to 60 °C. A glass and a sub-glass transition relaxations were observed in the dielectric spectra of PHBHHx. In addition, a nearly constant loss behavior was found by analyzing the dielectric and conductivity spectra.     

Electrospray multistep ion trap mass spectrometry for the structural characterisation of poly

Electrospray 'soft' ionisation (ESI) and multistep mass spectrometry (MS(n)) techniques enable characterisation of a bioactive polymer, poly[(R,S)-3-hydroxybutanoic acid] (a-PHB), containing covalently bonded benzylpenicillin. The chemical structures of individual mass-selected bioactive macromolecules have been determined, and their fragmentation mechanisms have been compared with those of pure penicillin G. Copyright 2000 John Wiley & Sons, Ltd.     

Electrospray mass spectrometry determination of poly(oxazolidine acetal)

The polycondensation of terephthalaldehyde with 2-amino-2-hydroxymethyl-1,3-propanediol (TRIS), or of terephthaldehyde with 2,2'-(1,4-phenylene)-bis-1,3-(4,4-dihydroxymethyl)oxazolidine (bis-oxazolidine), using acidic catalysts, leads to the formation of linear polymers and macrocyclic compounds. The structure of the polymer was determined by (1)H-, (13)C-NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS) analysis. ESI-MS measurements were used to study the details of the polymer structure and support the alternating nature of equimolar amounts of oxazolidine and the cyclic acetal of terephthaldehyde in these macromolecules.     

Improved mechanical property and biocompatibility of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) for blood vessel tissue engineering by blending with poly(propylene carbonate)

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) and poly(propylene carbonate) (PPC) were blended by solvent casting method into films at various weight ratios in order to obtain materials with properties more suitable for blood vessel tissue engineering than pure PHBHHx alone. FTIR and XRD analysis indicated the crystal structure of PHBHHx was not altered but the crystallinity was reduced by the interfusion of PPC. Mechanical properties of the films were improved significantly by blending with PPC. A lower elastic modulus and a higher elongation at break were obtained with the increase of PPC content. Wettability, fibronectin adsorption and adhesion of rabbit aorta smooth muscle cells (RaSMCs) on blend films were similar to or better than that on PHBHHx film. All these results showed promises of PHBHHx/PPC blended materials as scaffold material for blood vessel tissue engineering.     

Improvement of mechanical properties of poly(dl-lactide) films by blending of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) and poly(dl-lactide) (PDLLA) were blended at different ratios in an attempt to form a biomaterial with suitable properties for nerve regeneration. FT-IR and X-ray analysis showed that the blending of the PDLLA component did not alter the helical structure of PHBHHx, but did lead to a reduction of crystallinity. Differential scanning calorimetry (DSC) analysis indicated that the two polymers were immiscible in the melted state. The mechanical properties of certain composite films were more desirable than those of unblended PDLLA films. Blends consisting of PDLLA and PHBHHx at ratios of 2:1 and 1:2 exhibited a lower elastic modulus and a higher elongation at break compared to unblended PDLLA. ELISA results indicated that the amount of fibronectin adsorbed on composite films was much higher than the amount adsorbed on PDLLA film. The results of this study demonstrate the feasibility of using PDLLA/PHBHHx blended materials for biomedical applications.     

Electrospray ionisation tandem mass spectrometry in the characterisation of isomeric benzofurocoumarins

A set of aminoalkoxy-substituted, differently annullated furocoumarins, differing in the position of the aminoalkoxy chain and in the unsaturation level of the fused ring, has been subjected to electron impact and electrospray ionisation (ESI) experiments. In order to achieve a distinct characterisation of isomeric compounds, which partially failed under electron impact conditions, collision-induced dissociation experiments were performed on protonated molecules. The breakdown curves obtained by varying the tickle voltage on an ion trap ESI instrument led to the desired characterisation.     

Electrospray ionization tandem mass spectrometry for poly(propylene oxide) starting and end group analysis

Electrospray ionization tandem mass spectrometry was applied to study poly(propylene oxide) obtained in the presence of potassium hydride. It was found that the polyether chains possess different starting groups, i.e. those situated at the beginning of the polymer backbone. These were isopropoxy, hydroxy, methoxy and allyloxy groups when the polymerization was stopped by the addition of methyl iodide. Each macromolecule was terminated by the methoxy group in this case. Copyright 1999 John Wiley & Sons, Ltd.     

Isothermal crystallization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Isothermal crystallization behavior of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was investigated by means of differential scanning calorimetry and polarized optical microscopy (POM). The Avrami analysis can be used successfully to describe the isothermal crystallization kinetics of PHBV, which indicates that the Avrami exponent n=3 is good for all the temperatures investigated. The spherulitic growth rate, G, was determined by POM. The result shows that the G has a maximum value at about 353 K. Using the equilibrium melting temperature (448 K) determined by the Flory equation for melting point depression together with U∗=1500 cal mol⁻¹, T_∞=30 K and T_g=278 K, the nucleation parameter K_g was determined, which was found to be 3.14 ± 0.07 × 10⁵ (K²), lower than that for pure PHB. The surface-free energy σ=2.55×10⁻² J m⁻² and σ_e=2.70±0.06×10⁻² J m⁻² were estimated and the work of chain-folding (q=12.5±0.2 kJ mol⁻¹) was derived from σ_e, and found to be lower than that for PHB. This implies that the chains of PHBV are more flexible than that of PHB.     

Effects of metal ion-carbonyl interaction on miscibility and crystallization kinetic of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/lightly ionized PBS

Poly(butylene succinate) (PBS) and PBS-based ionomers (PBSi) with 1.0 and 3.0 mol% sodium sulfonate ionic group were synthesized and blended with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB-HHx) via direct melt compounding. FT-IR analysis demonstrated that the sodium metal ion–carbonyl interaction between PHB-HHx and PBS ionomer increased in strength with the ionic group concentration. Both non-isothermal and isothermal analyses showed the crystallization rates of PHB-HHx to decrease as the strength of the sodium metal ion–carbonyl interaction increased. However, the constant value obtained for the Avrami exponent indicated that the presence of PBS ionomer did not interfere in any way with the nucleation mechanism or the geometry of the crystal growth of PHB-HHx. DMTA analysis confirmed that PBS ionomer reduced the crystallinity of PHB-HHx, and this phenomenon increased in proportion to the ionic group content. As the ionic group concentration increased, the sodium metal–carbonyl interaction between PHB-HHx and PBS ionomer became much stronger, resulting in the improvement of the miscibility for the blend. The interaction parameter obtained by analyzing the equilibrium melting temperature was negative for all bend systems, with the ionomer having ionic group content, displaying a more negative value. Based on the Lauritzen–Hoffman secondary nucleation theory, the regime of the PHB-HHx/PBS ionomer blend remained unchanged throughout the crystallization process. In addition, both the nucleation constant and surface free energy were found to decrease as both ionomer content and ionic group concentration increased.     

Electrospray ionization, accurate mass measurements and multistage mass spectrometry experiments in the characterization of stereoisomeric isoquinoline alkaloids

Mass spectrometry has been employed for the characterization of diastereoisomeric isoquinoline alkaloids. Electrospray ionization was used to generate MH(+) ions, and multistage collisionally activated spectra allowed differentiation among the different compounds via specific fragmentation patterns, whose mechanisms have also been elucidated by accurate mass measurements.     

Macroporous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) matrices for cartilage tissue engineering

Polymer scaffold systems consisting of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) were investigated for possible application as a matrix for the three-dimensional growth of chondrocyte culture. The PHBV scaffolds were fabricated by a compression moulding, thermal processing and salt particulate leaching method without using organic solvent. The porous structure of the scaffolds was investigated with an optical microscope (OM) and scanning electron microscope (SEM) and the porosity was calculated. Then, the chondrocytes were cultured on the PHBV scaffolds for lone time to investigate whether it can be applied to construct the cartilage tissue in vitro. The results showed that the chondrocytes maintained their activity, fully expressed their phenotype and produced the extracellular matrix after incubation in vitro on the scaffolds for 7 days. In addition, in the prolonged incubation time, the percent of chondrocytes in their nature round morphology increased with an increase in the incubation period and they could synthesize the type II collagen and cartilage-specific proteoglycans. All of these results showed that the PHBV scaffolds had the potential to be used as chondrocytes carrier for cartilage engineering.     

Capillary electrophoresis-electrospray ion-trap mass spectrometry for the separation of chlorophenols

Eighteen positional isomers of chlorophenols were separated by capillary electrophoresis (CE) and detected on-line by electrospray ionization ion-trap mass spectrometry (MS). Conditions for the coupling of CE to MS, e.g., the concentration of carrier electrolyte, the sheath liquid composition and the sheath gas flow-rate were optimized. Diethylmalonic acid (5 mM) at pH 7.25 and isopropanol-250 mM dimethylamine (80:20) as sheath liquid were used. The activation parameters for ion-trap mass spectrometric analysis of chlorophenols were optimized. The mass spectra, obtained for all the analytes, revealed that the [M-H]- ion was the base peak for all chlorophenols. Moreover, conditions for CE-MS-MS detection were established and [M-H-HCl]- ions were detected.     

聚羟基丁酸酯共聚物超薄膜中向日葵晶形成的原子力显微镜观察

低维数下的高分子(如在二维薄膜或一维管道及孔洞中)的各种行为由于更加触及高分子的动力学、热力学本质而逐渐成为高分子科学研究的热点之一．实验表明,薄膜中聚合物的玻璃化转变温度、结晶动力学及形貌等与本体有很大的偏离．我们先前的研究结果表明,在基板的作用下,共混物薄膜的相形态会发生逆转;     

Production and characterization of poly(3-hydroxybutyrateco-3-hydroxyhexanoate)-poly(ethylene glycol) hybird copolymer with adjustable molecular weight

A novel natural-synthetic hybrid block copolymer was synthesized by Aeromonas hydrophila 4AK4 in poly(ethylene glycol)(PEG,M_n=200) modified fermentation.This hybrid biomaterial consists of the natural hydrophobic polymer poly(3-hydroxybutyrat-co-3-hydroxyhexanoate)(PHBHHx) end-capped with hydrophilic PEG,which has the increased flexibility as well as the improved thermal stability.Addition of diethylene glycol(DEG) and ethylene glycol could not result in the accumulation of hybrid block copolymer.DEG and ethylene glycol,together with PEG-200,could cause a reduction of molar mass of PHBHHx,resulting in a series of low molecular weight polymer and the reduction of the polymer yield as well as the cellular productivity.In vitro degradation of PHBHHx and PHBHHx-PEG with different molecular weight showed that the decrease of molecular weight accelerated the degradation of copolymers,but PEG modification has little effect on its degradation rate.The results in this study provided a convenient and direct method to produce a series of PHBHHx and PHBHHx-PEG materials with adjustable molecular weight and broad molecular weight distribution which will be very useful for the biomedical applications.     

Biosynthesis and compositional regulation of poly[(3-hydroxybutyrate)-co-(3-hydroxyhexanoate)] in recombinant ralstonia eutropha expressing mutated polyhydroxyalkanoate synthase genes

A new strategy for bacterial polyhydroxyalkanoate (PHA) production by recombinant Ralstonia eutropha PHB(-)4 harboring mutated PHA synthase genes (phaC(Ac)) from Aeromona caviae was investigated. The strain harboring wild-type phaC(Ac) gene produced a PHA copolymer consisting of (R)-3-hydroxybutyrate and (R)-3-hydroxyhexanoate [P(3HB-co-3HHx)] with 3.5 mol-% of 3HHx fraction from soybean oil. When the mutants of phaC(Ac) gene were applied to this production system, 3HHx fraction in copolymers was varied in the range of 0-5.1 mol-%. Thus, the regulation of PHA copolymer compositions has been achieved by the use of mutated PHA synthase genes.     

Inorganic mass spectrometry as a tool for characterisation at the nanoscale

Inorganic mass spectrometry techniques may offer great potential for the characterisation at the nanoscale, because they provide unique elemental information of great value for a better understanding of processes occurring at nanometre-length dimensions. Two main groups of techniques are reviewed: those allowing direct solid analysis with spatial resolution capabilities, i.e. lateral (imaging) and/or in-depth profile, and those for the analysis of liquids containing colloids. In this context, the present capabilities of widespread elemental mass spectrometry techniques such as laser ablation coupled with inductively coupled plasma mass spectrometry (ICP-MS), glow discharge mass spectrometry and secondary ion/neutral mass spectrometry are described and compared through selected examples from various scientific fields. On the other hand, approaches for the characterisation (i.e. size, composition, presence of impurities, etc.) of colloidal solutions containing nanoparticles by the well-established ICP-MS technique are described. In this latter case, the capabilities derived from the on-line coupling of separation techniques such as field-flow fractionation and liquid chromatography with ICP-MS are also assessed. Finally, appealing trends using ICP-MS for bioassays with biomolecules labelled with nanoparticles are delineated.      

Electrospray ionization mass spectrometry studies of rhenium(I) bipyridyl complexes

Electrospray ionization mass spectrometry (ESMS) has been employed to study the formation of fragment ions of a series of rhenium(I) bipyridyl complexes [(4,4'-di-(COOEt)2-bpy) Re(CO)3XPyPF6], where bpy is 2,2'-bipyridine, Py is pyridine, and X is H, 4-methyl, 3-methyl, 4-hydroxyl, 3-hydroxyl, 4-amino, or 3-amino of the pyridine ligand. The effects of substituents (X) on the stabilities of the complexes have been investigated with the increase of fragmentor voltages. For different X, the stabilities of the complexes increase as X become more electron-donating from H to CH3, OH, and NH2. For the same substituent, the p-substituted pyridines have stronger stabilizing effect than the corresponding m-substituted ones. Ligand exchange reaction was found in acetonitrile, where the pyridine ligand has been replaced by the solvent indicated by the formation of [M-PF6- XPy+MeCN]+ in the fragmentation.