Du Yumin

Preparation and anticoagulant activity of carboxybutyrylated hydroxyethyl chitosan sulfates

Abstract A new method of introduction carboxyl groups to chitosan sulfate by the acylation reaction between hydroxyethyl chitosan sulfates and butane dioic anhydride in homogeneous solution was used to obtain carboxybutyrylated hydroxyethyl chitosan sulfates. The structures of the derivatives were characterized by element analysis, FT-IR, 13 C-NMR, and gel permeation chromatography. The content and position of the carboxyl groups could be controlled favorably. Their anticoagulant activity was determined for human plasma with respect to activated partial thromboplastin time (APTT), thrombin time (TT), and prothombin time (PT). The introducing of carboxyl groups to amino groups greatly prolonged the APTT and TT. The best result occurred when the degree of substitution of the carboxyl groups was about 0.4/unit that prolonged APTT and TT with about 5 and 1.5 times compared to that of the uncarboxylated hydroxyethyl chitosan sulfates; another conclusion is that introducing of carboxyl groups into N , O -position gave better results than that just into N -positions. Low S% chitosan sulfate and 6- O -desulfated chitosan sulfate showed little anticoagulant activity but their N , O -carboxybutyrylated derivatives (0.6/unit ds) showed increased APTT or TT, while their N -carboxybutyrylated derivatives (0.6/unit ds) gave no improvement. Generally, the introducing of carboxyl groups could not increase PT in spite of the position introduced.

A new cross-linked quaternized-chitosan resin as the support of borohydride reducing agent

A new cross-linked resin was prepared by an inverse emulsion method under the protection of amino group. The resin reacted with glycidyl trimethylammonium chloride to form the quaternary ammonium ion resin, whose chloride was exchanged with potassium borohydride to get the borohydride exchange resin (CBER). CBER was used as a new polymer-supported reducing agent for the reduction of carbonyl compounds to corresponding alcohols, and exhibited a relatively high chemoselectivity and possessed the advantage of easy work-up.

Blend films of chitosan-gelatin

Chitosan-gelatin blend films were prepared successfully by solution method, and character- ized by FT-IR, X-ray diffraction, SEM, optical transmittance, percent water absorption and measure- ments of mechanical properties. The results indicated there was some strong interaction and good compati- bility between chitosan and gelatin molecule in the blend films. The introduction of chitosan was beneficial to decrease the percent water absorption ,improve mechanical properties of gelatin.

Swelling Studies of Chitosan.Gelatin Films Cross.Linked by Sulfate

Swelling properties of chitosan-gelatin films cross-linked by sulfate were investigated. Sulfate cross-linked chitosan-gelatin films (SCG) were prepared simply by dipping chitosan-gelatin films into sodium sulfate solution. The swelling behavior of SCG was investigated as a function of pH and ionic strength. Under acidic conditions pH less than 4, SCG swelled less than 120%, while under the conditions pH larger than 7.4, SCG swelled very significantly, the swelling ratio was over 350%. Sodium chloride weakened the electrostatic interaction between sulfate and amine ions of chitosan and gelatin, therefore facilitated the film swelling. The swelling ratio increased with increasing sodium chloride concentration, the SCG dissociated in the sodium chloride concentration of 0.20 mol·L−1. The parameters of film preparation such as sulfate concentration, dipping time, sulfate solution pH, influenced the film swelling behavior. The lower concentration and the higher pH of sulfate solution resulted in a larger swelling ratio.

Blend films of chitosan/starch

Chitosan-starch blend films were prepared, and their structure and properties were studied by FT-IR, X-ray diffraction, SEM and measurement of tensile strength. IR spectra and SEM analysis showed that the two polysaccharides were compatible, when the starch was less than 30% by weight. From X-ray diffraction patterns of blend fllms, it was observed that crystallization of starch was inhibited, and recrystallization of chitosan was also affected by starch. Crystal form I, one of the main two crystal forms of chitosan, drastically increased in 30% starch content films. These results indicated that the interactions between chitosan and starch molecules exist in the blend films. The tensile strength of the film were improved when chitosan and starch were blended by weight ratios of 8∶2 and 7∶3, in which the highest tensile strength (781 kg/cm2) was achieved.

Effect of Molecular Weight and Structure on Antitumor Activity of Oxidized Chitosan

Various low molecular weight chitosans were prepared by oxidative degradation with H2O2, and characterized by IR,13C-NMR and gel permeation chromatography. Their carboxylic contents increased with decrease in molecular weight (Mw). The antitumor test of the samples against sarcoma 180 tumors suggested that the water-soluble chitosan with higherMw have higher inhibitory ratioin vivo. The introduction of carboxylic group is advantage to water-solubility of chitosan, but more acidic groups might decrease the function of amino groups of chitosan against sarcoma 180 tumor.

Preparation and Characterization of Chitosan/Carboxymethylated Konjac Glucomannan Blend Films

In order to improve the mechanical and water swelling properties of the chitosan (CS) film, a series of transparent films were prepared by blending 2% (weight) chitosan acetic acid solution with 1.5% (weight) carboxymethylated konjac glucomannan (CMKGM) aqueous solution according to predetermined ratio and drying at 30°C. The morphological structure, miscibility, thermal stability, mechanical properies, and swelling capacity of the blend films were studied by infrared (IR), X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron micrograph (SEM), and measurements of the mechanical properties and swelling properties. The results demonstrated that there was strong interaction and good miscibility between CS and CMKGM resulted from intermolecular hydrogen bonding and electrostatic force. The mechanical properties in dry state and wet state, thermostability, and water swelling properties of the blend films were obviously improved. The best values of the tensile strength in the dry and wet state achieved 89 MPa and 49 MPa, respectively, when the CMKGM content was 30% (weight). The CS/ CMKGM blend films provided promising biomedical applications.

Solid-Phase Preparation and Characterization of Chitosan

Chitosan was prepared with stressing method by blending chitin and solid alkali in a single-screw extruder at given temperature and characterized by potentiometric titration, gel permeation chromatography (GPC), infrared spectrum (IR) and carbon-13 magnetic resonance sperctroscopy (13C NMR). Chitosan with a deacetylation degree (DD) of 76.1% was obtained at a mass ratio 0.2:1:1 for H2O/chitin/NaOH at 160°C for 12 min. Compared to conventional solution method(usually 1: 10 for chitin/NaOH), the alkali assumption greatly decreased. Molecular weight of chitosan obtained by solid-phase method (S3,Mw 1.54×105) was lower than that obtained by suspension method (Y2,Mw 3.34 ×105). During deacetylation, molecular weight decreased with high reaction temperature and long reaction time but remained same at different initial ratios of NaOH/chitin. It might be concluded that degradation of chitosan was caused by breakout of the main chain of the oxidized chitosan catalyzed by alkali during the deactylation. IR and13C NMR showed that structures of chitosans prepared by solid-phase method were not changed.

Studies of the reaction between laccase andp-phenylenediamime by microcalorimetry

l-In : W u h a n D a x u e X u e b a o ( Z i r a n K e x u e B a n ) , 1 9 9 7 , 4 3 ( 6 ) 9 741 ~ 7 4 6 ] STUDIES OF T H E R E A C T I O N B E T W E E N L A C C A S E A N D p P H E N Y L E N E D I A M I M E BY M I C R O C A L O R I M E T R Y Xie Xiuyin,Yan Chengnong,Wu Dingquan,Qu Shongsheng (Department of Chemistry, Wuhan University,Wuhan 430072,China) Du Yumin (Department of Environment Science, Wuhan University,Wuhan 430072 ,China) T h e m o l a r r e a t i on e n t h a l p y , t h e Michae l i s c o n s t a n t a n d the o b s e r v e d r a t e c o n s t a n t of t he r e a c t i o n bet w e e n the R h u s ve rn ic i f e ra l accase and p p h e n y l e n e d i a m i n e have been d e t e r m i n e d at 298. 15 K b y L K B 2107 m i c r o c a l o r i m e t r y s y s t e m in 0 . 1 m o l / L p h o s p h a t e sa l t b u f f e r (pHT. 4) to be A r H m = 1 3 6 . 3 6 q 0 . 36 k J / m o l , K ~ , = 5 . 5 8 X 10 -2 m o l / L and k ~ = 8 . 6 3 X 10-3s -1 , r e s p e c t i v e l y . T h e c a t a l y s t a c t i v i t y of l accase w i t h p p h e n y l e n e d i a m i n e as s u b s t r a t e has been d e t e r m i n e d to be E A ~ 0 . 045 I U in t he e x p e r i m e n t a l c o n d i t i o n . T h e o b s e r v e d ac t i va t i on e n e r g y of n o n e n z y m i c s t ep of the r e a c t i o n , t he G i b b s b i n d i n g e n e r g y of t he c o m b i na t i on p r o c e s s of laccase and s u b s t r a t e have been a lso c a l c u l a t e d . T h e p h y s i c a l s i gn i f i c a nc e of t he d e t e r mined p a r a m e t e r s were d i s c u s s e d for d i f f e r en t s t ep of t he r eac t i on . K e y w o r d s m i c r o c a l o r i m e t r y , r h u s ve rn ic i f e ra l a c c a s e , p p h e n y l e n e d i a m i n e , e n z y m a t i c r e a c t i o n

Studies on reduced extent method for inhibited thermokinetics of enzyme-catalyzed reaction

The thermokinetic reduced extent equations of reversible inhibitions for Michaiels-Menten enzymatic reaction were deduced, and then the criteria for distinguishing inhibition type was given and the methods for calculating kinetic parameters,KM,Ki andvm were suggested. This theory was applied to inverstigate the inhibited thermokinetics of laccase-catalyzed oxidation ofo-dihydroxybenzene bym-dihydroxybenzene. The experimental results show the inhibition belongs to reversible competitive type,KM=6.224×10−3 mol·L−1,Ki=2.363×10−2 mol·L−1.