Polyaniline: Synthesis and Natural Nanocomposites

Research and development in the field of conducting polymers can enable advancement in flexible electronics. Particularly polyaniline has been given importance due to stability, easy synthesis, reasonable conductivity and tunable properties by changing oxi dation states. We have presented a systematic study of effect polymerization time and temperature on polyaniline morphology and conductivity. It was noticed that with decrease in polymerization temperature and increase in polymerization duration, conducti vity of polyaniline increases. It was seen that particle size of polyaniline plays an important role in determining conductivity, irrespective of crystallinity, which suggests equal probability of electron conduction along and between the polyaniline chain s. The highest conductivity obtained was for 24 hours of polymerisation in temperature ( - 18 ̊ C). Conducting polymers including polyaniline possess poor mechanical properties. Cellulosic materials were chosen as substrate because of abundance, bio compatibility, biodegradability, and low cost. . Polyaniline was impregnated into corn cob cover by in sit u polymerization to prepare composite. The conductivity was measured to be 8×10 - 4 S/cm for 15 % of polyaniline in the sample. Bacterial cellulose was chosen as another substrate because of its purity, mechanical properties and tenability. Composites of poly aniline and bacterial cellulose were also made by in situ polymerization. Three types of bacterial celluloses with variation in microstructure and porosity were used. The best conductivity was found to be 2×10 - 3 S/cm for over 50% of polyaniline

The nanoscale organization of the B lymphocyte membrane

AbstractThe fluid mosaic model of Singer and Nicolson correctly predicted that the plasma membrane (PM) forms a lipid bi-layer containing many integral trans-membrane proteins. This model also suggested that most of these proteins were randomly dispersed and freely diffusing moieties. Initially, this view of a dynamic and rather unorganized membrane was supported by early observations of the cell surfaces using the light microscope. However, recent studies on the PM below the diffraction limit of visible light (~250nm) revealed that, at nanoscale dimensions, membranes are highly organized and compartmentalized structures. Lymphocytes are particularly useful to study this nanoscale membrane organization because they grow as single cells and are not permanently engaged in cell:cell contacts within a tissue that can influence membrane organization. In this review, we describe the methods that can be used to better study the protein:protein interaction and nanoscale organization of lymphocyte membrane proteins, with a focus on the B cell antigen receptor (BCR). Furthermore, we discuss the factors that may generate and maintain these membrane structures

Synthesis Time and Temperature Effect on Polyaniline Morphology and Conductivity

This paper studies the effect of time and temperature of polymerisation on morphology and conductivity of polyaniline which is produced by oxidative polymerisation. It has been reported that with decrease in temperature and increase in polymerisation duration, the yield and particle size increases. The polyaniline particles are rod-like at the onset of polymerisation and also at low polymerisation temperature. The conductivity has been determined by four-point measurement with incorporation of correction factor. It was found that the electrical conductivity varies from below 0.5 S/cm to over 11 S/cm with variation in duration and temperature of polymerization. Conductivity is proposed to be dependent on the particle size as conductivity increases with decrease in polymerisation temperature and increase in polymerisation duration, similar to the trend observed for particle size. This may be indicative of equal probability of inter- chain and intra-chain charge transport

cAMP Stringently Regulates Human Cathelicidin Antimicrobial Peptide Expression in the Mucosal Epithelial Cells by Activating cAMP-response Element-binding Protein, AP-1, and Inducible cAMP Early Repressor*

Little is known about the regulation of the innate host defense peptide cathelicidin at the mucosal surfaces. Expression is believed to be transcriptionally regulated, and several cis-acting elements have been identified in the cathelicidin putative promoter. However, the trans-acting factors have not been clearly defined. We have recently reported that bacterial exotoxins suppress cathelicidin expression in sodium butyrate-differentiated intestinal epithelial cells (ECs), and this may be mediated through inducible cAMP early repressor. Here we have shown that cAMP-signaling pathways transcriptionally regulate cathelicidin expression in various ECs. cAMP-response element-binding protein (CREB) and AP-1 (activator protein-1) bind to the cathelicidin putative promoter in vitro. Additionally, transcriptional complexes containing CREB, AP-1, and cathelicidin upstream regulatory sequences are formed within ECs. We have also shown that these complexes may activate cathelicidin promoter and are required for its inducible expression in ECs. This is underscored by the fact that silencing of CREB and AP-1 results in failure of ECs to up-regulate cathelicidin, and hepatitis B virus X protein may use CREB to induce cathelicidin. On the other hand, inducible cAMP early repressor competes with CREB and AP-1 for binding to the cathelicidin promoter and represses transcription, thus functioning as a counter-regulatory mechanism. Finally, both CREB and AP-1 were shown to play major roles in the regulation of cathelicidin in sodium butyrate-differentiated HT-29 cells. This is the first report of a detailed mechanistic study of inducible cathelicidin expression in the mucosal ECs. At the same time, it describes a novel immunomodulatory function of cAMP