Affinity membrane chromatography for the analysis and purification of proteins

Affinity chromatography is unique among separation methods as it is the only technique that permits the purification of proteins based on biological functions rather than individual physical or chemical properties. The high specificity of affinity chromatography is due to the strong interaction between the ligand and the proteins of interest. Membrane separation allows the processing of a large amount of sample in a relatively short time owing to its structure, which provides a system with rapid reaction kinetics. The integration of membrane and affinity chromatography provides a number of advantages over traditional affinity chromatography with porous-bead packed columns, especially with regard to time and recovery of activity. This review gives detailed descriptions of materials used as membrane substrates, preparation of basic membranes, coupling of affinity ligands to membrane supports, and categories of affinity membrane cartridges. It also summarizes the applications of cellulose/glycidyl methacrylate composite membranes for proteins separation developed in our laboratory.

Capillary electrochromatography for separation of peptides driven with electrophoretic mobility on monolithic column

A mode of capillary electrochromatography for separation of ionic compounds driven by electrophoretic mobility on a neutrally hydrophobic monolithic column was developed. The monolithic column was prepared from the in situ copolymerization of lauryl methacrylate and ethylene dimethacrylate to form a C12 hydrophobic stationary phase. It was found that EOF in this hydrophobic monolithic column was very poor, even the pH value of mobile phase at 8.0. The peptides at acidic buffer were separated on the basis of their differences in electrophoretic mobility and hydrophobic interaction with the stationary phase; therefore, different separation selectivity can be obtained in CEC from that in capillary zone electrophoresis (CZE). Separation of peptides has been realized with high column efficiency (up to 150,000 plates/meter) and good reproducibility (migration time with RSD <0.5%), and all of the peptides, including some basic peptides, showed good peak symmetry. Effects of the mobile phase compositions on the retention of peptides at low pH have been investigated in a hydrophobic capillary monolithic column. The significant difference in selectivity of peptides in CZE and CEC has been observed. Some peptide isomers that cannot be separated by CZE have been successfully separated on the capillary monolithic column in this mode with the same buffer used.

Chromatographic separation of proteins on metal immobilized iminodiacetic acid-bound molded monolithic rods of macroporous poly(glycidyl methacrylate-co-ethylene dimethacrylate)

Continuous rod of macroporous poly(glycidyl methacrylate-co-ethylene dimethacrylate) was prepared by a free radical polymerization within the confines of a stainless-steel column. The epoxide groups of the rod were modified by a reaction with iminodiacetic acid (IDA) that affords the active site to form metal IDA chelates used for immobilized metal affinity chromatography (IMAC). The efficiency of coupling of IDA to the epoxide-contained matrix was studied as a function of reaction time and temperature. High-performance separation of proteins, based on immobilized different metals on the column, were described. The influence of pH on the adsorption capacity of bovine serum albumin on the Cu2+-IDA continuous rod column was investigated in the range from 5.0 to 9.0. Purification of lysozyme from egg white and human serum albumin (HSA) on the commercially available HSA solution were performed on the naked IDA and Cu2+-IDA continuous rod columns, respectively; and the purity of the obtained fractions was detected by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry.

[Relationship between methylenetetrahydrofolate reductase gene polymorphism and diabetic nephropathy]

OBJECTIVE

To investigate the relationship between methylenetetrahydrofolate reductase(MTHFR) gene polymorphism and diabetic nephropathy(DN).

METHODS

The technology of polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) was used to detect MTHFR gene C677T mutation in 85 healthy controls, 79 type-2 diabetics without DN, and 82 type-2 diabetics with DN confirmed by urine microalbuminous detection.

RESULTS

The frequencies of MTHFR gene variant genotypes and alleles in the patients with DN patients were significantly higher than those in the patients without DN and those in healthy controls (P<0.01).

CONCLUSION

MTHFR gene C677T mutation is probably one of the genetic risk factors for diabetic nephropathy in Chinese Hans.

Invited review: arteriolar smooth muscle mechanotransduction: Ca(2+) signaling pathways underlying myogenic reactivity

The smooth muscle of arterioles responds to an increase in intraluminal pressure with vasoconstriction and with vasodilation when pressure is decreased. Such myogenic vasoconstriction provides a level of basal tone that enables arterioles to appropriately adjust diameter in response to neurohumoral stimuli. Key in this process of mechanotransduction is the role of changes in intracellular Ca(2+). However, it is becoming clear that considerable complexity exists in the spatiotemporal characteristics of the Ca(2+) signal and that changes in intracellular Ca(2+) may play roles other than direct effects on the contractile process via activation of myosin light-chain phosphorylation. The involvement of Ca(2+) may extend to modulation of ion channels and release of Ca(2+) from the sarcoplasmic reticulum, alterations in Ca(2+) sensitivity, and coupling between cells within the vessel wall. The purpose of this brief review is to summarize the current literature relating to Ca(2+) and the arteriolar myogenic response. Consideration is given to coupling of Ca(2+) changes to the mechanical stimuli, sources of Ca(2+), involvement of ion channels, and spatiotemporal aspects of intracellular Ca(2+) signaling.

Coupling of a P2Z-like purinoceptor to a fatty acid-activated K(+) channel in toad gastric smooth muscle cells

1. Extracellular application of ATP generates two whole-cell currents in toad gastric smooth muscle cells: an immediate inward non-selective cation current (due to the activation of a P2X or P2Z-like receptor) and a slowly developing outward K(+) current. The inward non-selective cation current depends on the continuous presence of ATP while the outward K(+) current can last for minutes after ATP application ceases. 2. In cell-attached patches, application of ATP to the extra-patch membrane can activate K(+) channels in the patch indicating that a diffusible cellular messenger may be involved. The characteristics of these K(+) channels are similar to those of a previously described fatty acid-activated K(+) channel that is also a stretch-activated channel. 3. This whole-cell K(+) current can be induced by ATP in the absence of extracellular Ca(2+) (with EGTA present to chelate trace amounts). However, the current generated in the presence of extracellular Ca(2+) is considerably larger. 4. The pharmacological profiles for the activation of the non-selective cation current and the K(+) current are similar, suggesting that the same P2Z-like receptor could be mediating both responses. This type of plasma membrane receptor/channel-channel coupling by a process that does not appear to involve Ca(2+) flow through the receptor/channel or a subsequent membrane potential change may be representative of a new class of signalling mechanisms.

Therapeutic antitumor response to cervical cancer in mice immunized with U14 vaccines transfected with costimulatory B7 gene

OBJECTIVE

To investigate the effect of U14 vaccine transfected with the B7 gene in inducing antitumor immune response to murine cervical carcinoma in Chinese 615-strain mice.

METHODS

A recombinant retroviral plasmid vector expressing mouse B7-1 gene (pLNSX-mB7) was transfected into 615-strain mouse cervical carcinoma cell line No. 14 (U14) by electroporation to set up a highly-expressed mB7-1 U14 cell clonal strain (B7+ U14). In vivo experiments: (1) B7+ U14 vaccine was primed to protect the 615-strain mice against U14 re-challenge. (2) B7+ U14 vaccine was injected into tumor-bearing mice with different tumor sizes. Lifetimes and tumor sizes were recorded. In vitro cytotoxicity assay: Mice were immunized with B7+ U14 or U14 vaccine and 2 weeks later, spleen cells of those mice were cultured for 2 days. The cytotoxicity of these cells against U14 was detected by 5-diphenyl tetrazolium bromide assay.

RESULTS

We obtained several B7-1 high expression clonal U14 lines. In vivo experiment, we did not find tumor growing in 3 of the 6 mice primed by B7+ U14 vaccine during their entire life after re-challenge with U14. The other 3 mice developed tumors and their average survival time was longer than that of the control group (P < 0.01). All 6 mice grew tumors in the control group. When the transplanted tumors became palpable, the mice were randomly divided into 3 groups to be injected with B7+ U14 vaccine. It was effective for tumor-bearing mice only when the tumor diameters were < 3 mm. When the diameters were > or = 3 mm, it was not efficacious to inject B7+ U14 vaccine (P < 0.05). In vitro cytotoxicity assay, cytotoxic T lymphocytes induced by B7+ U14 vaccine had a higher cytotoxicity against U14 than that induced by U14 vaccine (F = 310.8, P < 0.001).

CONCLUSIONS

Vaccines of cervical cancer cells transfected with the costimulatory molecule B7 gene can induce antitumor immune protection in host mice against U14 re-challenge. This treatment may cure part of the tumor-bearing mice but be restricted by tumor size. The results suggest that transfecting the B7 gene into cervical cancer as a cell vaccine may be an efficient supplementary method to treat cervical cancer after operation.

[Clinical analysis of 62 cases laryngeal papilloma in children]

OBJECTIVE

To investigate the clinical features of laryngeal papilloma in children.

METHOD

In a group of 62 patients with laryngeal papilloma in children, the tumors of 28 patients were cut under the direct laryngoscope, 34 patients were treated with laryngeal micro-laser operation.

RESULT

The post-operation followup ranged from 2 to 5 years, the cure rate of 2 years was 51.61%.

CONCLUSION

The clinical features of this disease include rapid development, a large lesion, and it is often found in the infraglottic cavity. Furthermore, we believe that in order to eliminate the tumors more accurately and decrease recurrence, micro-laser surgery and the use of interferon is very necessary.

Determination of the hydrophobicity of local anesthetic agents

Hydrophobicity, a term used to describe a fundamental physicochemical property of local anesthetics, was in the past obtained by octanol/buffer partitioning. It has been suggested that the octanol method, despite its obvious advantages, also has some drawbacks. HPLC has become an attractive alternative for the measurement of hydrophobicity and has been applied to local anesthetics recently. However, the methods in current use for measuring the hydrophobicity of local anesthetics suffer from a number of limitations and remain obscure. This study introduces a new HPLC method for measuring the hydrophobicity of eight local anesthetics in current clinical use. Using a C(18) derivatized polystyrene-divinylbenzene stationary phase HPLC column, the log k'(w) values of local anesthetics were determined by measuring the capacity factor k'(i) in the process of chromatographic separation using a hydrophobic stationary phase and a hydrophilic mobile phase. A rapid reversed-phase HPLC method was developed to directly measure log k'(w) of eight local anesthetics. A high correlation between log k'(w) and hydrophobicity (log P(oct)) from the traditional shake-flask method was obtained for the local anesthetics, demonstrating the reliability of the method. The results reveal an improved method for measuring the hydrophobicity of the local anesthetic agents in the unionized form. This simple, sensitive and reproducible approach may serve as a valuable tool for describing the physicochemical properties of novel local anesthetics.

Separation of 4-dimethylamino-6-(4-methoxy-1-naphthyl)-1,3,5-triazine-2-hydrazine derivatives of carbonyl compounds by reversed-phase capillary electrochromatography

4-Dimethylamino-6-(4-methoxy-1-naphthyl)-1,3,5-triazine-2-hydrazine (DMNTH) is a novel derivatizing reagent specially designed for the determination of carbonyl compounds. In this work, we describe the separation of DMNTH-derivatized carbonyl compounds by reversed-phase capillary electrochromatography (CEC). After systematic investigations of the effects of experimental conditions viz. pH and concentration of buffer, type of stationary phase, injection volume of sample, organic modifier, and temperature, optimal conditions were found. The sample compounds, which were separated with gradient high performance liquid chromatography (HPLC), were separated by CEC under isocratic elution due to the high efficiency. Comparisons of separations by CEC and micellar electrokinetic chromatography (MEKC) were made.

A cyclic voltammetry method suitable for characterizing antioxidant properties of wine and wine phenolics

Phenolic antioxidants are ranked by reducing strength and characterized for reversibility using cyclic voltammetry at a glassy carbon electrode. Phenolics with an ortho-diphenol group show a first oxidation peak close to 400 mV (vs. Ag/AgCl) in a model wine solution (12% ethanol, 0.033 M tartaric acid, adjusted to pH 3.6), with a linear concentration dependence below 0.01 mM. Dilution of white wines 10x, and red wines 400x, gave first oxidation peak currents in the 1.5 to 2.2 microA range and 1.9 to 3.4 microC of charge passed by 500 mV, producing values for the concentrations of phenolic antioxidants with low oxidation potentials in the wines. Further peaks in the cyclic voltammograms of the diluted wines correspond to classes of phenolics with higher oxidation potentials, providing a qualitative assessment of wine phenolics based on reducing strength.

Analysis of bioactive components in traditional Chinese medicines by molecular biochromatography with alpha1-acid glycoprotein stationary phase

Molecular biochromatography with alpha1-acid glycoprotein (AGP) stationary phase was proposed to screen and analyse the biologically active components in traditional Chinese medicines (TCMs) with extracts from Radix Salviae miltiorrhizae as a tested sample. More than ten peaks were resolved based on their affinity to AGP. The effects of concentrations of acetonitrile, pH, concentration of inorganic salt and temperature on the retention behaviors of several major active components were also investigated, and it was found that the hydrophobic effect is the major contributor to retention. Tanshinone IIA was identified as one of the principal bioactive components, which is the marker for the quality control of Radix Salviae miltiorrhizae and a complicated remedy named YiXiTongMai. The amount of tanshinone IIA in Radix Salviae miltiorrhizae and YiXiTongMai determined by this method was 2.9 mg/g (net weight, RSD 4.9%, n=5) and 0.078 mg/g (net weight, RSD 2.5%, n=3), respectively. The possibility for fast differentiation of the TCM sources was also studied by the comparison of the fingerprint of chromatograms for eight typical TCMs on the AGP column. It was observed that different TCMs showed different fingerprint characteristics. Even for the same plant, Rhizoma cimicifugae from three different geographical sources, although there were common characteristics, distinct differences in types and concentrations of biologically active components were clearly observed. It was shown that molecular biochromatography was an effective and fast way for the analysis and screening of biologically active compounds in traditional Chinese medicines.

Separation of basic, acidic and neutral compounds by capillary electrochromatography using uncharged monolithic capillary columns modified with anionic and cationic surfactants

A mode of capillary electrochromatography (CEC), based on the dynamical adsorption of surfactants on the uncharged monolithic stationary phases has been developed. The monolithic stationary phase, obtained by the in situ polymerization of butyl methacrylate with ethylene dimethacrylate, was dynamically modified with an ionic surfactant such as the long-chain quaternary ammonium salt of cetyltrimethylammonium bromide (CTAB) and long-chain sodium sulfate of sodium dodecyl sulfate (SDS). The ionic surfactant was adsorbed on the surface of polymeric monolith by hydrophobic interaction, and the ionic groups used to generate the electroosmotic flow (EOF). The electroosmotic mobility through these capillary columns increased with increasing the content of ionic surfactants in the mobile phase. In this way, the synthesis of the monolithic stationary phase with binary monomers can be controlled more easily than that with ternary monomers, one of which should be an ionic monomer to generate EOF. Furthermore, it is more convenient to change the direction and magnitude of EOF by changing the concentration of cationic or anionic surfactants in this system. An efficiency of monolithic capillary columns with more than 140000 plates per meter for neutral compounds has been obtained, and the relative standard deviations observed for to and retention factors of neutral solutes were about 0.22% and less than 0.56% for ten consecutive runs, respectively. Effects of mobile phase composition on the EOF of the column and the retention values of the neutral solutes were investigated. Simultaneous separation of basic, neutral and acidic compounds has been achieved.

Enantiomer separation by strong anion-exchange capillary electrochromatography with dynamically modified sulfated beta-cyclodextrin

A novel mode of capillary electrochromatography (CEC) based on a dynamically modified stationary phase was presented for chiral separation. The capillary column was packed with strong anion-exchange (SAX) stationary phase packing; the sulfated beta-cyclodextrin (S-CD), which was added to the mobile phase, was dynamically adsorbed to the packing surface. Separation of enantiomers was achieved by their different abilities to form an inclusion complex with the adsorbed S-CD. The enantiomers of tryptophan, praziquantel, atropine, metoprolol, and verapamil were successfully separated in this system with a column efficiency of 36000-412000 plates/m. The resolution value obtained for atropine was as high as 11.23. The superiority of CEC with a dynamically modified stationary phase over that with a physically adsorbed stationary phase was demonstrated. The influence of ionic strength, S-CD concentration, and methanol content on separation was also studied.

[Anti-tumor immune response to cervical carcinoma induced by costimulatory molecule B7 gene in mice]

OBJECTIVE

To investigate the effects of B7 costimulatory molecule on inducing anti-tumor immune response to cervical carcinoma in vivo.

METHODS

We transfected mouse B7 gene into murine cervix carcinoma cell line U14 by electroporation, and obtained several high-expressed mB7 U14 cell clonal strains (B7+ U14) detected by reverse transcription polymerase chain reaction (RT-PCR). In vivo experiments: (1) 1 x 10(7) B7+ U14 cells were inoculated into the back of inbred 615-strain mice by subcutaneously injection to determine their tumorigenicity (n = 6). (2) The mice primed by B7+ U14 (1 x 10(6)) cells were re-challenged with 1 x 10(7) wild type U14 to observe the immune protection of these mice against the wild type U14 (n = 6). As control, (3) wild type U14 cells were inoculated the same as the experimental group (1) (n = 6). (4) The mice both primed and re-challenged with 1 x 10(7) wild type U14 the same as the experimental group (2) (n = 6). All mice lifetime and tumor sizes were recorded. In vitro cytotoxiaty assay: the mice were immunized with B7+ U14 or the wild type U14 by intraperitoneal injection (n = 4 x 2) and two weeks late those mice spleen cells were obtained and cultured for two days. The cytotoxiaty of these cells against the wild U14 was detected by methyl thiazolyl tetrazolium assay.

RESULTS

RT-PCR showed positive results in B7+ U14 cells, while negative in U14 cells. In vivo experiment: (1) after the inoculation of the B7+ U14 cells into the back of inbred mice, they lost their tumorigenicity greatly compared to wild type U14 (P < 0.01). (2) Primed by B7+ U14, mice protected themselves effectively against rechallenged (P < 0.01). In vitro cytotoxiaty assay, the cytotoxic T lymphocytes (CTLs) induced by B7+ U14 had a higher cytotoxiaty against the wild type U14 than that induced by wild type U14 (P < 0.01).

CONCLUSIONS

Cervical carcinoma cells transfected with constimulatory molecules B7 gene can decrease their tumorigenicity greatly, and induce anti-tumor immune protection of inbred mice against wild type U14 cells re-challenged. The results suggest that to transfect B7 gene into cervical cancer expression may be an effect method for treating cervical cancer in clinical.

Structured data management--the design and implementation of a web-based video archive prototype

In response to the lack of readily available multimedia rich medical knowledge sources to support medical education and patient care, we designed and implemented a web-based video publishing platform. In order to promote the development of high-quality, up-to-date educational content, we have devised a scalable structure that allows online submissions and continuous updating of video and accompanying textual descriptions. Our goal is to enable experts in varied medical domains to collaborate in the construction of a video library using an intuitive web-based interface. Neurologists at Stanford built a well-annotated neurology video collection that initially emphasized childhood and adult movement disorders. The collection may be accessed either as a stand-alone resource or as part of the Stanford Skolar MD, an integrated online medical knowledge provider. This manuscript discusses the design framework and implementation details of structured media content development. We present examples illustrating media data collection, content indexing using UMLS concepts, media storage, and web presentation.

Immunomodulatory effects of acupuncture in the treatment of allergic asthma: a randomized controlled study

OBJECTIVE

According to Traditional Chinese Medicine (TCM) acupuncture is a suitable treatment for complex chronic diseases such as bronchial asthma. In a randomized, controlled study we investigated immunologic effects of Chinese acupuncture on patients with allergic asthma.

PATIENTS AND METHODS

The effects of acupuncture treatment given according to the principles of TCM (TCM group, n = 20) were compared with those of acupuncture treatment using points not specific for asthma (control group, n = 18). All patients were treated 12 times for 30 minutes over a time period of 4 weeks. Patients' general well-being and several peripheral blood parameters (eosinophils, lymphocyte subpopulations, cytokines, in vitro lymphocyte proliferation) were determined before and after acupuncture treatment.

RESULTS

In the TCM group, significantly more patients indicated an improvement in general well-being (79% in the TCM group versus 47% in the control group; p = 0.049) after acupuncture treatment. The following changes were found in the TCM group: within the lymphocyte subpopulations the CD3+ cells (p = 0.005) and CD4+ cells (p = 0.014) increased significantly. There were also significant changes in cytokine concentrations: interleukin (IL)-6 (p = 0.026) and IL-10 (p = 0.001) decreased whereas IL-8 (p = 0.050) rose significantly. Additionally, the in vitro lymphocyte proliferation rate increased significantly (p = 0.035) while the number of eosinophils decreased from 4.4% to 3.3% after acupuncture (p > 0.05). The control group, however, showed no significant changes apart from an increase in the CD4+ cells (p = 0.012).

CONCLUSION

The results imply that asthma patients benefit from acupuncture treatment given in addition to conventional therapy. Furthermore, acupuncture performed in accordance with the principles of TCM showed significant immune-modulating effects.

Study on open tubular capillary affinity liquid chromatography

A novel mode of affinity chromatography (AC) based on an open tubular capillary column (OTAC) is demonstrated. The OTAC column is prepared by immobilizing Cibacron blue F3GA onto the inner surface of a 50-microm-i.d. capillary column. The AC experiment is performed on a capillary electrophoresis instrument by using its pressure system as the driving force. Bovine serum albumin and lysozyme (Lys) are successfully separated with stepwise gradient elution. The relative standard deviation (RSD) for the elution time of the retained Lys is 0.08%, and good repeatability of its peak area and peak height with an RSD value lower than 2.12% for 10 consecutive runs is observed. The loading capacity and detection limit for the retained Lys are approximately 36 ng and 8.6 ng, respectively. It is also found that the amount of protein adsorbed is unaffected by the flow rate of the loading buffer, and OTAC can be used for the fast determination of biopolymers. Some of the advantages of OTAC over conventional modes of open tubular capillary liquid chromatography are that the detection sensitivity and loading capacity of a sample can be greatly improved, because the relatively large inner diameter of the capillary can be adopted and the whole capillary column can be used to adsorb the solute in OTAC.

Capillary electrochromatography with physically and dynamically absorbed stationary phases

Adsorption is always considered a troublesome effect in capillary electrophoresis (CE) and capillary electrochromatography (CEC). However, the adsorption effect can also be exploited to prepare or optimize the stationary phase in CEC. Compared with the chemical synthesis of new stationary phase materials for CEC, this method is simpler and more convenient. This review is focused on CEC with physically and dynamically adsorbed stationary phases. Separation of some acidic, basic and neutral solutes as well as enantiomers in CEC with dynamically adsorbed stationary phases are presented. The theory for the migration of charged solutes and the stationary phases currently used in CEC are also briefly reviewed.

Alkaline treatment of the cellulose fiber affecting membrane column behaviour for high-performance immunoaffinity chromatography

The original cellulose fibers and those treated by alkaline solution were both used to prepare the acrylic membranes. The two kinds of membranes were packed into the columns for high-performance immunoaffinity chromatography by the immobilization of protein A on them. It was observed that the alkaline treatment of the cellulose fiber decreased the pressure resistance of the membrane to the mobile phases and greatly increased the accessible volume to the proteins, but affected the adsorption capacity of human IgG on the protein A membrane columns less. There is little difference between those two kinds of membranes on the adsorption capacities of HIgG, which means that the alkaline treatment of the cellulose fiber only significantly changes the void volume inter-membrane, and the porosity and surface area of membrane less. Alkaline treatment of the cellulose fiber reduced the membrane-column efficiency significantly. Some typical examples for the immunoaffinity analysis of IgG from human and dog plasma on the protein A membrane columns are illustrated.

On-line characterization of the activity and reaction kinetics of immobilized enzyme by high-performance frontal analysis

A microreactor by immobilized trypsin on the activated glycidyl methacrylate-modified cellulose membrane packed column was constructed. Immobilized trypsin mirrored the properties of the free enzyme and showed high stability. A novel method to characterize the activity and reaction kinetics of the immobilized enzyme has been developed based on the frontal analysis of enzymatic reaction products, which was performed by the on-line monitoring of the absorption at 410 nm of p-nitroaniline from the hydrolysis of N-alpha-benzoyl-DL-arginine-p-nitroanilide (BAPNA). The hydrolytic activity of the immobilized enzyme was 55.6% of free trypsin. The apparent Michaelis-Menten kinetics constant (Km) and Vmax values measured by the frontal analysis method were, respectively, 0.12 mM and 0.079 mM min(-1) mg enzyme(-1). The former is very close to that observed by the static and off-line detection methods, but the latter is about 15% higher than that of the static method. Inhibition of the immobilized trypsin by addition of benzamidine into substrate solution has been studied by the frontal analysis method. The apparent Michaelis-Menten constant of BAPNA (Km), the inhibition constant of benzamidine (Ki) and Vmax were determined. It was indicated that the interaction of BAPNA and benzamidine with trypsin is competitive, the Km value was affected but the Vmax was unaffected by the benzamidine concentration.

Synthesis and characteristics of the human serum albumin-triazine chiral stationary phase

Human serum albumin (HSA) was successfully bonded to silica with s-triazine as activator. The coupling reaction by this method was rapid and effective. The triazine-activated silica is relatively stable and can be installed for at least 1 month without obvious loss of reactivity when stored below 30 degrees C, pH below 7. It was observed that the amount of bound HSA reached 120 mg/g silica calculated from the UV absorbance difference of the HSA solution. d, l-tryptophan was selected as the probe solute to characterize the properties of HSA bonded s-triazine chiral stationary phase, and separation factor of 9.4 was obtained for d,l-tryptophan. Furthermore, the amount of effective HSA on silica was measured by high-performance frontal analysis, and only 16.8 mg/g silica was responsible for the resolution of d,l-tryptophan. These results indicate that the amount of both the bound and effective HSA on silica with triazine as activator was much higher than those by the Schiff base coupling method. Different kinds of enantiomers were resolved successfully on the aminopropylsilica-bonded HSA s-triazine chiral stationary phase.