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C Chains (c + chain)
Selected AbstractsBiochemical and functional characterization of the interaction between pentraxin 3 and C1qEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 2 2003Abstract Pentraxin 3 (PTX3) is a recently characterized member of the pentraxin family of acute-phase proteins produced during inflammation. Classical short pentraxins, C-reactive protein, and serum amyloid P component can bind to C1q and thereby activate the classical complement pathway. Since PTX3 can also bind C1q, the present study was designed to define the interaction between PTX3 and C1q and to examine the functional consequences of this interaction. A dose-dependent binding of both C1q and the C1 complex to PTX3 was observed. Experiments with recombinant globular head domains of human C1q A, B, and C chains indicated that C1q interacts with PTX3 via its globular head region. Binding of C1q to immobilized PTX3 induced activation of the classical complement pathway as assessed by C4 deposition. Furthermore, PTX3 enhanced C1q binding and complement activation on apoptotic cells. However, in the fluid-phase, pre-incubation of PTX3 with C1q resulted in inhibition of complement activation by blocking the interaction of C1q with immunoglobulins. These results indicate that PTX3 can both inhibit and activate the classical complement pathway by binding C1q, depending on the way it is presented. PTX3 may therefore be involved in the regulation of the innate immune response. [source] Monolayers of sulfur-containing molecules at metal surfaces as studied using SERS: 3, 3,-thiodipropionic acid and 3-mercaptopropionic acid adsorbed on silver and copperJOURNAL OF RAMAN SPECTROSCOPY, Issue 6-7 2005Andrzej Kudelski Abstract The modification of metal surfaces with self-assembled thiol monolayers is the subject of intensive studies owing to both its fundamental interest in surface chemistry and its potential technological significance. In this work, the applicability of surface-enhanced Raman scattering (SERS) to determine the conformation and pKa values of ,-terminated thiol molecules was investigated. 3, 3,-Thiodipropionic acid (TDPA) and 3-mercaptopropionic acid (MPA) monolayers were spontaneously formed on silver and copper surfaces by adsorption from TDPA and MPA solutions, respectively. The structure of the monolayers formed was determined from SERS measurements. The SERS investigations showed that molecules forming TDPA monolayers prefer to adopt a gauche conformation of the,S,C,C chains, whereas in MPA monolayers formed from 1 mM MPA aqueous solution a significant part of the adsorbed molecules adopts a trans conformation. Formation on the metal surface of an MPA monolayer with high surface coverage of MPA makes dissociation of the carboxylic groups of MPA significantly more difficult. Analogous changes in the strength of similar adsorbed compounds have been reported by other groups. In contrast to those results, we found that the formation of monolayers from TDPA increases its acidic strength even at high surface coverage when monolayers are formed from relatively concentrated TDPA solutions. Probably the interaction of carboxylic groups with the metal surface is easier for TDPA than for MPA for geometric reasons. We consider that ionization of carboxylic groups increases the strength of this interaction. Copyright © 2005 John Wiley & Sons, Ltd. [source] One-dimensional surface states induced by segregated impurities at transition-metal surfacesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2006G. Trimarchi Abstract Using ab initio pseudopotential calculations, we have investigated the atomic and electronic structure of a c (3,2 × ,2) striped reconstruction, induced by segregated C impurities, at the Fe(001) surface. The segregated C atoms form zigzag chains, which in turn produce one-dimensional Fe surface states near the Fermi energy. We address the influence of the C chains on the local surface atomic geometry, local electrostatic potential, and local density of states, and discuss the formation mechanism of the one-dimensional surface states. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Chain-length specificities of maize starch synthase I enzyme: studies of glucan affinity and catalytic propertiesTHE PLANT JOURNAL, Issue 5 2001Padmavathi D. Commuri Summary It is widely known that some of the starch synthases and starch-branching enzymes are trapped inside the starch granule matrix during the course of starch deposition in amyloplasts. The objective of this study was to use maize SSI to further our understanding of the protein domains involved in starch granule entrapment and identify the chain-length specificities of the enzyme. Using affinity gel electrophoresis, we measured the dissociation constants of maize SSI and its truncated forms using various glucans. The enzyme has a high degree of specificity in terms of its substrate,enzyme dissociation constant, but has a greatly elevated affinity for increasing chain lengths of ,-1, 4 glucans. Deletion of the N-terminal arm of SSI did not affect the Kd value. Further small deletions of either N- or C-terminal domains resulted in a complete loss of any measurable affinity for its substrate, suggesting that the starch-affinity domain of SSI is not discrete from the catalytic domain. Greater affinity was displayed for the amylopectin fraction of starch as compared to amylose, whereas glycogen revealed the lowest affinity. However, when the outer chain lengths (OCL) of glycogen were extended using the phosphorylase enzyme, we found an increase in affinity for SSI between an average OCL of 7 and 14, and then an apparently exponential increase to an average OCL of 21. On the other hand, the catalytic ability of SSI was reduced several-fold using these glucans with extended chain lengths as substrates, and most of the label from [14C]ADPG was incorporated into shorter chains of dp < 10. We conclude that the rate of catalysis of SSI enzyme decreases with the OCL of its glucan substrate, and it has a very high affinity for the longer glucan chains of dp ,20, rendering the enzyme catalytically incapable at longer chain lengths. Based on the observations in this study, we propose that during amylopectin synthesis shorter A and B1 chains are extended by SSI up to a critical chain length that soon becomes unsuitable for catalysis by SSI and hence cannot be elongated further by this enzyme. Instead, SSI is likely to become entrapped as a relatively inactive protein within the starch granule. Further glucan extension for continuation of amylopectin synthesis must require a handover to other SS enzymes which can extend the glucan chains further or for branching by branching enzymes. If this is correct, this proposal provides a biochemical basis to explain how the specificities of various SS enzymes determine and set the limitations on the length of A, B, C chains in the starch granule. [source] Expression and structure of interleukin 4 receptors in primary meningeal tumorsCANCER, Issue 10 2005Sachin Puri M.Sc. Abstract BACKGROUND It was reported previously that malignant human tumors, like glioma and medulloblastoma, express high-density interleukin (IL-4) receptor mRNA and protein. Because IL-4 receptors (R) are sensitive targets for targeted therapeutics, knowledge of the expression of these receptors in other central nervous system tumors is of great interest. In this study, the authors examined the expression and subunit composition of IL-4R complex in primary human meningiomas. METHODS Reverse transcription-polymerase chain reaction (RT-PCR) analysis for IL-13R,1, IL-4R, and IL-2R,c was performed on total RNA extracted from 35 meningiomas and a normal human brain tissue sample. Results were confirmed in nine randomly selected tumors by quantitative real-time PCR and in situ immunofluorescence assay. RESULTS Transcripts for the IL-4R, and IL-13R,1 chains were overexpressed in meningiomas compared with normal brain tissue. The levels of IL-4R, mRNA appeared to be higher compared with the levels of IL-13R,1 mRNA. The results also showed that tumors with higher disease grade tended to have increased mRNA expression for the IL-4R, chain. This IL-4R, mRNA overexpression appeared to be more frequent in younger patients (age < 37 years). The transcripts for IL-2R,c chain were not detected in any of the tumor samples or in normal brain tissue. Quantitative real-time PCR confirmed the results of the RT-PCR analysis. Meningiomas also demonstrated a bright immunofluorescent staining for the IL-4R, and IL-13R,1 chains but no staining for IL-2R,c. CONCLUSIONS Expression of the IL-4R, and IL-13R,1 chains and absence of IL-2,c expression established that meningiomas expressed type II IL-4Rs. These receptors may serve as a target for cytotoxin/immunotoxin therapy in patients with meningioma who are not amenable to surgical resection or for recurrent tumors. Cancer 2005. © 2005 American Cancer Society. [source] | ||||||||||