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The emergence of adaptive immunity in jawed vertebrates depended on the appearance of variable immune receptors, BCRs and TCRs, which exhibit variable-J–constant (VJ-C)–type Ig superfamily folds. Hitherto, however, the structures of IgV-J-IgC–type molecules had never been characterized in invertebrates, leaving the origin of BCR/TCR-type molecules unknown. Using x-ray crystallography, the structure of a VJ-C2 molecule, named AmpIgVJ-C2, was determined in amphioxus (Branchiostoma floridae). The first domain shows typical V folding, including the hydrophobic core, CDR analogs, and eight conserved residues. The second domain is a C2-type Ig superfamily domain, as defined by its short length and the absence of β-strand D- and C1-typical motifs. AmpIgVJ-C2 molecules form homodimers, using “three-layer packing dimerization,” as described for TCRs and BCRs. The AmpIgVJ-C2 V domain harbors a diglycine motif in β-strand G and forms a β-bulge structure participating in V–V intermolecular interaction. By immunohistochemistry, AmpIgVJ-C2 molecules were primarily found in mucosal tissues, whereas PCR and sequence analysis indicated considerable genetic variation at the single-gene level; these findings would be consistent with an immune function and a basic ability to adapt to binding different immune targets. Our results show a BCR/TCR-ancestral like molecule in amphioxus and help us to understand the evolution of the adaptive immune system.

Novel biodegradable amphiphilic graft copolymers containing hydrophobic poly(ester-carbonate) backbone and hydrophilic poly(ethylene glycol) (PEG) side chains were synthesized by a combination of ring-opening polymerization and “click” chemistry. First, the ring-opening copolymerization of 5,5-dibromomethyl trimethylene carbonate (DBTC) and e-caprolactone (CL) was performed in the presence of stannous octanoate [Sn(Oct)2] as catalyst, resulting in poly(DBTC-co-CL) with pendant bromo groups. Then the pendant bromo groups were completely converted into azide form, which permitted “click” reaction with alkyne-terminated PEG by Huisgen 1,3-dipolar cycloadditions to give amphiphilic biodegradable graft copolymers. The graft copolymers were characterized by proton nuclear magnetic resonance (1H NMR), Fourier transform infrared spectra and gel permeation chromatography measurements, which confirmed the well-defined graft architecture. These copolymers could self-assemble into micelles in aqueous solution. The size and morphologies of the copolymer micelles were measured by transmission electron microscopy and dynamic light scattering, which are influenced by the length of PEG and grafting density. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.

Alginate with long strictly alternating sequences of mannuronic (M) and guluronic (G) acid residues, F(G) = 0.47 and F(GG) = 0.0, was prepared by incubating mannuronan with the recombinant C-5 epimerase AlgE4. By partial acid hydrolysis of this PolyMG alginate at pH values from 2.8 to 4.5 at 95 degrees C, alpha-L-GulpA-(1--4)-beta-D-ManpA (G-M) linkages were hydrolyzed far faster than beta-D-ManpA-(1--4)-alpha-L-GulpA (M-G) linkages in the polymer chain. The ratio of the rates (kG-M/kM-G) decreased with increasing pH. The dominant mechanism for hydrolysis of (1--4)-linked PolyMG in weak acid was thus proved to be an intramolecular catalysis of glycosidic cleavage of the linkages at C-4 by the undissociated carboxyl groups at C-5 in the respective units. The higher degradation rate of G-M than M-G glycosidic linkages in the polymer chain of MG-alginate at pH 3.5 and 95 degrees C was exploited to make oligomers mainly consisting of M on the nonreducing and G on the reducing end and, thus, a majority of oligomers with an even number of residues. The ratio of the rate constants kG-M/kM-G at this pH was 10.7. The MG-hydrolysate was separated by size exclusion chromatography and the MG oligosaccharide fractions analyzed by electrospray ionization-mass spectrometry together with 1H and 13C NMR spectroscopy. Chemical shifts of MG-oligomers (DP2-DP5) were elucidated by 2D 1H and 13C NMR.

It was demonstrated that macroscopic structural changes of polysaccharide chains, such as random coil–helix transition and aggregation of helices, accompanied with the sol–gel and the gel–sol transition can be monitored by numerically analyzing the temperature dependence of the observed water proton spin–spin relaxation time ( T 2obs ) modified by the chemical exchange between water proton and labile proton on the chain. According to the numerical analysis of T 2obs , typical profiles of T 2obs against the temperature were simulated with various parameters of the relaxation time ( T 2 i ) and the mean residence time ( τ i ) of water and the labile protons on the random coil and the ordered chain as well as the activation energy ( E i , E ex, i ) for the motion and the chemical exchange of the respective proton. The difference of structural change of kappa- , iota- , and lambda-carrageenan aqueous systems in the cooling and the heating process was analyzed. In conclusion, (1) the characteristic profile of the temperature dependence of T 2obs , commonly observed in the temperature-induced gelling process, is attributable to the variation of fraction of the ordered chain and the relative rate of chemical exchange to the relaxation rate of labile protons on polysaccharide (1/ T 2p ); (2) the loose aggregated or associated structure is detected for iota-carrageenan system; and (3) the thermally stable junction zones formed by well aggregated helices of kappa-carrageenan in the gel state provokes a thermal hysteresis in the temperature-induced structural change (experimentally, in T 2obs ). It is clarified by the numerical simulation that the aggregated helices formed during further cooling down to the temperature below T sg results in the T 2obs shifts to a longer value in the heating process as compared with that in the cooling process.

In this work, two series of ethylene–dimethylaminoethylmethacrylate (EDAM) and ethylene–methyl acrylate copolymers (EMA) with different comonomer content were studied by high-resolution solid-state 13 C NMR spectroscopy. Biexponential 13 C spin–lattice relaxation behaviors of the crystalline region were observed for all copolymer samples either melt-quenched or isothermally crystallized. The relative content of the shorter 13 C T 1 component to that of the longer 13 C T 1 component was found to increase with comonomer content. By employing a new pulse sequence which can be considered as a combination of Goldman–Shen's and Torchia's pulse sequences, it was demonstrated that the shorter 13 C T 1 component is corresponding to the intermediate part of the crystalline region. The thickness of the intermediate part is estimated to be about 0.85 nm.

The phase structure of a series of ethylene-vinyl acetate copolymers has been investigated by solid-state wide-line 1H NMR and solid-state high-resolution 13C NMR spectroscopy. Not only the degree of crystallinity but the relative contents of the monoclinic and orthorhombic crystals within the crystalline region varied with the vinyl acetate (VA) content. Biexponential 13C NMR spin–lattice relaxation behavior was observed for the crystalline region of all samples. The component with longer 13C NMR spin–lattice relaxation time (T1) was attributed to the internal part of the crystalline region, whereas the component with shorter 13C NMR T1 to the mobile crystalline component was located between the noncrystalline region and the internal part of the crystalline region. The content of the mobile crystalline component relative to the internal part of the crystalline region increased with the VA content, showing that the 13C NMR spin–lattice relaxation behavior is closely related to the crystalline structure of the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2199–2207, 2002

The crystalline structures of ethylene-dimethylaminoethyl methacrylate (EDAM) copolymers, which were either melt-quenched (mq) or isothermally crystallized (iso), were studied by solid-state high-resolution 13 C NMR spectroscopy. It revealed that the crystalline structures of EDAM copolymers are greatly dependent on the comonomer content, crystallization condition and the storage time after treatment. The ratio of monoclinic to orthorhombic crystal (M/O) increases with the increase in the dimethylaminoethyl methacrylate content. Higher crystallinity and lower monoclinic content were observed for iso samples compared to the mq ones. The monoclinic crystal was found to melt at lower temperatures compared to the orthorhombic one during the heating process. The degree of crystallinity as well as the contents of monoclinic and orthorhombic crystals and the M/O value are found to increase after storage at room temperature for a month.

To study the anti-tumor activity of Scurrula parasitica polysaccharides (SP). Water extraction and ethanol precipitation were used to isolate SP from S. parasitica leaf. S180, K562 and HL-60 cell lines proliferation inhibition by SP were detected by MTT assay. The expressions of Ki-67, Cyclin D1, Bax and Bcl-2 protein in the sarcoma S180 tissues were detected by immunohistochemistry technique to approach the anti-tumor mechanism of SP+ SP could not inhibit cancer cell proliferation. SP ip could inhibit the growth of sarcoma S180 in mice, 100 mg x kg(-1) x d(-1). SP ip was the optimal dose on inhibiting S180 growth, with the tumor inhibition rate of 54%. The expression of Ki-67, Cyclin D1, Bax and Bcl-2 protein in the sarcoma S180 tissues were detected by immunohistochemistry technique to approach the anti-tumor mechanism of SP. The result showed that SP could down-regulate the expression of Ki-67, CyclinD1 and Bcl-2 protein, and up-regulate the expression of Bax protein. It indicted that inhibiting cancer cell proliferation and promoting cancer cell apoptosis in vivo maybe one of the anti-cancer mechanisms of SP.

Biodegradable antimicrobial poly(ester-carbonate)s were prepared facilely via a simple two-step process with low cost. First, poly(5,5-dibromomethyl trimethylene carbonate-co-e-caprolactone) (PDBTCL) with pendant bromo groups was synthesized by the direct ring-opening copolymerization of 5,5-dibromomethyl trimethylene carbonate (DBTC) and e-caprolactone (CL) in the presence of stannous octanoate (Sn(Oct)2) as catalyst. Then, the quaternization reaction between PDBTCL and a series of N,N-dimethyl alkylamines was performed under mild conditions, resulting in biodegradable poly(ester-carbonate)s with pendant ammonium salts (QPDBTCL). The chemical structure and composition of QPDBTCLs were characterized by 1H NMR. The influences of alkyl chain length and charge density on the antimicrobial activity of QPDBTCLs against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria were evaluated by OD600 and zone of inhibition methods. It was observed that QPDBTCLs with long alkyl chain on the ammonium groups exhibit significantly higher antimicrobial activity than those with short alkyl chain for both Gram-negative and Gram-positive bacteria. QPDBTCL with quaternary N,N-dimethyldodecylammonium groups shows strong antimicrobial activity even with very low charge density (4.3 mol%). This kind of biodegradable antimicrobial material may have potential applications as biomaterials.