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Zhongwu Guo

Publications and source records attributed to Zhongwu Guo.

At least 19 recordsLinked to original sources
PubMed2006

Cap and capture-release techniques applied to solid-phase synthesis of oligosaccharides.

This paper reports a new strategy for oligosaccharide synthesis by combining solid-phase methods with cap and capture-release separation techniques, using the p-(5-(ethoxycarbonyl)pentyloxy)benzyl group (CPB) as a tag for the capture of desired oligosaccharides. After a complex carbohydrate mixture was obtained by solid-phase synthesis, the desired oligosaccharide containing a free carboxyl group derived from CPB was attached to an amino resin. The loaded resin was readily separated from side products by filtration and finally treated with acid to release the pure oligosaccharide product.

Carbohydrate Conformation↗
PubMed2006

Streptococcus agalactiae CAMP factor binds to GPI-anchored proteins.

CAMP factor (protein B) is a pore-forming protein secreted by Streptococcus agalactiae. It causes lysis of sheep red blood cells when these have been sensitized with staphylococcal sphingomyelinase. We here show that CAMP factor binds to GPI-anchored proteins, and that this interaction involves the carbohydrate core of the GPI-anchor. Enzymatic cleavage of GPI-anchors with phosphatidylinositol-specific phospholipase C strongly reduces the sensitivity of erythrocytes to CAMP factor. Incorporation of alkaline phosphatase, a model GPI-anchored protein, into liposome membranes renders the latter susceptible to permeabilization by CAMP factor. GPI-anchored proteins therefore function as cellular receptors for CAMP factor.

Bacterial Proteins↗
PubMed2006

Efficient metabolic engineering of GM3 on tumor cells by N-phenylacetyl-D-mannosamine.

Abnormal carbohydrates expressed on tumor cells, which are termed tumor-associated carbohydrate antigens (TACAs), are potential targets for the development of cancer vaccines. However, immune tolerance to TACAs has severely hindered progress in this area. To overcome this problem, we have developed a novel immunotherapeutic strategy based on synthetic cancer vaccines and metabolic engineering of TACAs on tumor cells. One critical step of this new strategy is metabolic engineering of cancer, namely, to induce expression of an artificial form of a TACA by supplying tumors with an artificial monosaccharide precursor. To identify the proper precursor for this application, N-propionyl, N-butanoyl, N-isobutanoyl, and N-phenylacetyl derivatives of d-mannosamine were synthesized, and their efficiency as biosynthetic precursors in modifying sialic acid and inducing expression of modified forms of GM3 antigen on tumor cells was investigated. For this purpose, tumor cells were incubated with different N-acyl-d-mannosamines, and modified forms of GM3 expressed on tumor cells were analyzed by flow cytometry using antigen-specific antisera. N-Phenylacetyl-d-mannosamine was efficiently incorporated in a time- and dose-dependent manner to bioengineer GM3 expression by several tumor cell lines, including K562, SKMEL-28, and B16-F0. Moreover, these tumor cell lines also exhibited ManPAc-dependent sensitivity to cytotoxicity mediated by anti-PAcGM3 immune serum and complement. These results provide an important validation for this novel therapeutic strategy. Because N-phenylacetyl GM3-protein conjugates are particularly immunogenic, the combination of an N-phenylacetyl GM3 conjugate vaccine with systemic N-phenylacetyl-d-mannosamine treatment is a promising immunotherapy for future development and application to melanoma and other GM3-bearing tumors.

Animals↗
PubMed2005

Surface modification of liposomes by saccharides: vesicle size and stability of lactosyl liposomes studied by photon correlation spectroscopy.

The cell glycocalyx is an attractive model for surface modification of liposomes, because its hydrated oligosaccharide layer inhibits nonspecific protein adsorption and can provide specificity towards desired sites. Here, we report on the use of lactose as a model saccharide to modify the liposome surface and examine the vesicle size and stability. Two kinds of lactosyl lipids, including lactosyl ether-lipid (6a) and lactosyl ester-lipid (6b), which contain octadecyl and octadecanoyl as the lipid tails, respectively, were synthesized and their liposomes were prepared by the extrusion method. The effects of glycolipid structure, concentration, and the pore size of the extrusion membrane on vesicle size and stability were investigated at room temperature by photon correlation spectroscopy (PCS). All liposomes with 5 or 10 mol% of lactosyl lipids had a narrow size distribution and remained stable at room temperature for at least one month, which is comparable to 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)- and poly(ethylene glycol) (PEG)-liposomes. The maximum incorporation of lactosyl ester-lipid into liposomes was 15 mol%, compared with only 10 mol% for the lactosyl ether-lipid. The lactosyl ester-liposomes had better stability and exhibited less size change than the lactosyl ether-liposomes at 15 or 20 mol% of lactosyl lipids incorporated. This may be attributed to the better structural compatibility of lactosyl ester-lipid with DSPC. The PCS results show that the glycolipid structure and concentrations are major factors that affect vesicle stability, while the pore size of extrusion membranes has no influence.

Carbohydrate Conformation↗
PubMed2005

Pentaerythritol as the core of multivalent glycolipids: synthesis of a glycolipid with three SO3Lea ligands.

A glycolipid containing three SO(3)Le(a) ligands was synthesized with pentaerythritol as the core. The glycolipid was used to prepare glycoliposomes that showed stability similar to that of DSPC liposomes without glycolipid. The easily prepared derivatives of pentaerythritol proved to be useful scaffolds for multivalent displaying of carbohydrates in the form of glycolipids and clustered glycoliposomes. [structure: see text]

Carbohydrate Sequence↗
PubMed2005

Solution-phase synthesis with solid-state workup of an O-glycopeptide with a cluster of cancer-related T antigens.

An N-terminal glycopeptide of asialoglycophorin AM with three O-linked T antigens was prepared by "solution-phase synthesis with solid-state workup" using unprotected glycosyl amino acids as building blocks. For the glycopeptide assembly, all reactions were conducted in homogeneous NMP solutions, while the product of each reaction was readily isolated as solid precipitates upon addition of diethyl ether. In the preparation of building blocks, a robust approach was established to selectively alpha-glycosylate Ser and Thr derivatives. [reaction: see text]

Amino Acids↗
PubMed2005

Synthesis and immunological properties of N-modified GM3 antigens as therapeutic cancer vaccines.

The problem of immunotolerance to GM3, an important tumor-associated trisaccharide antigen, seriously hinders its usage in cancer vaccine development. To solve this problem, the keyhole limpet hemocyanin (KLH) conjugates of a series of GM3 derivatives were synthesized and screened as therapeutic cancer vaccines. First, the beta-linked anomeric azides of differently N-acylated GM3 analogues were prepared by a highly convergent procedure. Next, a pentenoyl group was linked to the reducing end of the carbohydrate antigens following selective reduction of the azido group. The linker was thereafter ozonolyzed to give an aldehyde functionality permitting the conjugation of the antigens to KLH via reductive amination. Finally, the immunological properties of the resultant glycoconjugates were studied in C57BL/6 mice by assessing the titers of specific antibodies induced by the GM3 analogues. While KLH-GM3 elicited low levels of immune response, the KLH conjugates of N-propionyl, N-butanoyl, N-iso-butanoyl, and N-phenylacetyl GM3s induced robust immune reactions with antibodies of multiple isotypes, indicating significantly improved and T-cell dependent immune responses that lead to isotype switching, affinity maturation, and the induction of immunological "memory". It was suggested that GM3PhAc-KLH is a promising vaccine candidate for glycoengineered immunotherapy of cancer with GM3 as the primary target.

Animals↗
PubMed2005

Glycopeptide and glycoprotein synthesis involving unprotected carbohydrate building blocks.

This review summarizes the chemical and chemoenzymatic synthesis of glycopeptides and glycoproteins using unprotected carbohydrates as key intermediates. The synthetic methods covered herein include the convergent synthesis of glycopeptides by chemoselective ligation of peptides and free glycans, solution- and solid-phase synthesis of glycopeptides by sequential peptide elongation with unprotected glycosyl amino acids or short glycopeptides as building blocks, and the synthesis of glycopeptides by enzymatic and/or chemical elongation of the free glycans. The use of unprotected carbohydrates in these syntheses can circumvent the final-stage carbohydrate deprotection, lead to highly convergent synthetic designs, and more significantly, take advantage of the commercially available free glycans isolated from nature, which could considerably facilitate the synthesis of complex glycopeptides and glycoproteins.

Amino Acid Sequence↗
PubMed2005

[A study of gait recognition based on kinematics and kinetics parameters].

In order to recognize people by their gait, we propose a pattern recognizing method based on kinematics and kinetics parameters. The feature extraction methods of joint angle and vertical ground reaction force (VGRF) were given. 14 healthy male subjects participated in this experiment. The experimental results showed that the correct classification rates (CCR) was 87.1% at k = 1 and 90% at k = 3 (k-nearest neighbor) based on joint angle recognition; the CCR was 85.7% at k = 1 and 80% at k = 3 based on VGRF recognition. The multivariate analysis of the experimental data proved the feasibility of gait recognition. The principal component analysis and curves of VGRF also showed that the instant of foot strike plays an important role in gait recognition.

Adult↗
PubMed2005

[Algorithm for recognizing the markers in human motion detection].

An algorithm for recognizing the markers in human motion detection is proposed in this paper. It includes three parts as follows: (1) an improved template matching method is used to acuminate the peak of the matching result. (2) The weighted average of the cross correlation between target image and template is given in order to make the resolution increase to sub-pixel level. (3) Forecasting the motion of marker and overcoming the hiding of marker are realized basing on the continuity of human motion. The result of experiments shows that the algorithm can recognize the positions of the markers at a relatively higher accuracy and speed. A gait analysis system based on this algorithm has come into use.

Algorithms↗
PubMed2004

Accessibility of N-acyl-D-mannosamines to N-acetyl-D-neuraminic acid aldolase.

N-Acetyl-D-neuraminic acid (NeuNAc) aldolase is an important enzyme for the metabolic engineering of cell-surface NeuNAc using chemically modified D-mannosamines. To explore the optimal substrates for this application, eight N-acyl derivatives of D-mannosamine were prepared, and their accessibility to NeuNAc aldolase was quantitatively investigated. The N-propionyl-, N-butanoyl-, N-iso-butanoyl-, N-pivaloyl-, and N-phenylacetyl-D-mannosamines proved to be as good substrates as, or even better than, the natural N-acetyl-D-mannosamine, while the N-trifluoropropionyl and benzoyl derivatives were poor. It was proposed that the electronic effects might have a significant influence on the enzymatic aldol condensation reaction of D-mannosamine derivatives, with electron-deficient acyl groups having a negative impact. The results suggest that N-propionyl-, N-butanoyl-, N-iso-butanoyl-, and N-phenylacetyl-D-mannosamines may be employed to bioengineer NeuNAc on cells.

Carbohydrate Conformation↗
PubMed2004

A new reaction for the direct conversion of 4-azido-4-deoxy-D-galactoside into a 4-deoxy-D-erythro-hexos-3-ulose.

[reaction: see text] A new one-step reaction has been developed for converting 4-azido-4-deoxy-d-galactoside into 4-deoxy-d-erythro-hexos-3-ulose by phosphoramidites and tetrazole. It is proposed that the new reaction proceeds via an intramolecular Staudinger reaction of the phosphite intermediate and a tetrazole-catalyzed elimination reaction of the resultant phosphorimidate. Tetrazole appears to be playing a unique role by acting as a bifunctional catalyst to facilitate the elimination reaction.

Azides↗
PubMed2004

Vaccination of small cell lung cancer patients with polysialic acid or N-propionylated polysialic acid conjugated to keyhole limpet hemocyanin.

PURPOSE: Long chain polysialic acid (polySA) is a side chain on embryonal neural cell adhesion molecules that, in the adult, is largely restricted to small cell lung cancer (SCLC). Long chains of polySA are also expressed on group B meningococcus. In this clinical trial, we aimed to elicit an immune response against polysialic acid to target clinically inapparent residual disease in patients with SCLC who had successfully completed initial therapy. EXPERIMENTAL DESIGN: Patients were vaccinated with either 30 micro g unmodified polySA or N-propionylated-polySA (NP-polySA), conjugated to keyhole limpet hemocyanin (KLH) and mixed with 100 micro g of immunological adjuvant QS-21 at weeks 1, 2, 3, 4, 8, and 16. RESULTS: Of the 5 evaluable patients vaccinated with unmodified polySA, only 1 mounted an IgM antibody response to polySA. On the other hand, all 6 of the patients vaccinated with NP-polySA produced IgM antibodies to NP-polySA and these cross-reacted with unmodified polySA in all but 1 case. IgG antibodies to NP-polySA were observed in 5 of the patients, but these did not cross-react with polySA. The presence of IgM antibodies reactive with SCLC cell lines was confirmed in this group by flow cytometry. Complement-dependent lysis of tumor cells could not be demonstrated. However, postimmunization sera induced significant bactericidal activity against group B meningococcus when combined with rabbit complement. CONCLUSIONS: Vaccination with NP-polySA-KLH, but not polySA-KLH, resulted in a consistent high titer antibody response. We are now conducting a de-escalation dosing study with NP-polySA-KLH to better assess the immunogenicity, toxicities, and optimal dose of this vaccine. We plan to incorporate this vaccine as a component of a polyvalent vaccine with GM2, fucosylated GM1, and Globo H to target SCLC.

Adjuvants, Immunologic↗
PubMed2004

Preparation and immunological studies of protein conjugates of N -acylneuraminic acids.

The overexpression of N -acetylneuraminic acid (Neu5Ac) is closely correlated with malignant transformations. Thus, Neu5Ac is an important target in the design of cancer vaccines. To study the influence of chemical modifications of Neu5Ac on its immunological properties, the alpha-allyl glycosides of five differently N -acylated neuraminic acid derivatives were prepared. Following selective ozonolysis of their allyl group to form an aldehyde functionality, they were coupled to keyhole limpet hemocyanin (KLH) via reductive amination. Resultant glycoconjugates were studied in C57BL/6 mice. The N -propionyl, N - iso- butanoyl and N -phenylacetyl derivatives of neuraminic acid provoked robust immune responses of various antibody isotypes, including IgM, IgG1, IgG2a and IgG3, whereas N -trifluoropropionylneuraminic acid and natural Neu5Ac were essentially nonimmunogenic. Moreover, the N -phenylacetyl and N - iso- butanoyl derivatives mainly induced IgG responses that are desirable for antitumor applications. These results raise the promise of formulating effective glycoconjugate cancer vaccines via derivatizing sialic acid residues of sialooligosaccharides.

Animals↗
PubMed2003

Convergent synthesis of a GPI containing an acylated inositol.

A GPI of sperm CD52 was synthesized by a highly convergent procedure, representing the first chemical synthesis of a complex GPI having an acylated inositol. The presence of a large acyl group resulted in unusual properties and reactions of the relevant intermediates, which gave rise to a number of problems. To overcome the problems and achieve the target molecule, a new synthetic strategy was developed. First, the pseudodisaccharide of 2-O-palmitoylinositol was phospholipidated, and then the trimannose segment and the phosphoethanolamine group were sequentially attached. Global deprotection eventually afforded the sperm CD52 GPI. The method may be useful for the synthesis of other GPIs having an acylated inositol.

Acylation↗
PubMed2003

Chemical synthesis of CD52 glycopeptides containing the acid-labile fucosyl linkage.

Glycopeptide 1 with the fucosylated trisaccharide, beta-d-GlcNAc(1-->4)[alpha-l-Fuc(1-->6)]-beta-d-GlcNAc, linked to the Asn of CD52 peptide was prepared by two methods, both of which used the free glycosyl Asn 12 and glycotripeptide 21 as key intermediates. Thus, after the trisaccharide was prepared and linked to Asn, the carbohydrate moiety was deprotected to give 12. From 12, 21 was constructed in homogeneous NMP solutions by elongating the peptide chain alone the N-terminus. Though the glycopeptides were easily soluble in NMP, they were barely soluble in diethyl ether, because of the free trisaccharide. Consequently, addition of diethyl ether to the reaction mixtures could precipitate the glycopeptides, and the products were conveniently isolated and purified in the solid form. The coupling of 21 with a free nonapeptide 24 in NMP afforded 1. 1 was also prepared by solid-phase synthesis, using the acid-sensitive 2-chlorotrityl resin. In this case, 21 was attached to the nonapeptide on the resin, and the resulting glycopeptide was then released with dilute acetic acid. Deprotection of the peptide under moderate acidic conditions gave 1. The acid-labile alpha-fucose was not affected in these syntheses.

Acids↗
PubMed2003

First total synthesis of a GPI-anchored peptide.

A GPI-anchored dipeptide of sperm CD52 antigen was prepared through a convergent synthesis. First, the dipeptide with its C-terminus free and the GPI with its nonreducing end phosphoethanolamine bearing a free amino group were synthesized separately. Then, the two building blocks were coupled with use of EDC/HOBt as the condensation reagent. Finally, the GPI-anchored peptide was deprotected to give the target molecule 1.

Antigens, CD↗