Self-assembly of surfactant aqueous solution confined in a Janus amphiphilic nanotube

Abstract

In recent years, Janus amphiphilic nanotubes with complex surfaces have been synthesized. However, the self-assembly behaviour of surfactant solutions confined in a Janus amphiphilic nanotube has not been investigated so far. We performed molecular simulations to investigate the morphologies and phase diagrams of a surfactant confined in Janus amphiphilic nanotube consisting of both hydrophobic and hydrophilic surfaces. We derived a phase diagram of the representative snapshots of equilibrium morphologies. Morphologies that were not observed in the bulk eventuated in confined systems. Moreover, the self-assembled structures were found to be dependent on the spatial confinement. Furthermore, the self-assembled structures confined in hydroneutral and Janus amphiphilic nanotubes were compared. The results suggested that the self-assembled structures confined in the Janus amphiphilic nanotube resembled that confined in the hydroneutral nanotube owing to a strong confinement effect. Further developments in controlling the morphologies and self-assemblies will greatly advance their applications of these materials in nanofluidic devices, or for nanopatterning.     

Design, synthesis, and evaluation of novel kazusamycin A derivatives as potent antitumor agents

Novel kazusamycin A derivatives were designed in the viewpoint of decrease of reactivity at the alpha,beta-unsaturated delta-lactone moiety against Michael-type addition. Although 25-30 steps were required for the synthesis of each compound, their syntheses were achieved. Cytotoxicity against HPAC cell line was evaluated, and two of them exhibited comparable potency to kazusamycin A. Hepatic toxicity of these designed compounds was much lower than that of kazusamycin A.     

Characterization of acatalasemic erythrocytes treated with low and high dose hydrogen peroxide. Hemolysis and aggregation

The effects of hydrogen peroxide on normal and acatalasemic erythrocytes were examined. Severe hemolysis of acatalasemic erythrocytes and a small tyrosine radical signal (g = 2.005) associated with the formation of ferryl hemoglobin were observed upon the addition of less than 0.25 mM hydrogen peroxide. However, when the concentration of hydrogen peroxide was increased to 0.5 mM, acatalasemic erythrocytes became insoluble in water and increased the tyrosine radical signal. Polymerization of hemoglobin and aggregation of the erythrocytes were observed. On the other hand, normal erythrocytes exhibited only mild hemolysis by the addition of hydrogen peroxide under similar conditions. From these results, the scavenging of hydrogen peroxide by hemoglobin generates the ferryl hemoglobin species (H-Hb-Fe(IV)=O) plus protein-based radicals (*Hb-Fe(IV)=O). These species induce hemolysis of erythrocytes, polymerization of hemoglobin, and aggregation of the acatalasemic erythrocytes. A mechanism for the onset of Takarara disease is proposed.     

High level expression, purification, and characterization of the shrimp antimicrobial peptide, Ch-penaeidin, in Pichia pastoris

Penaeidins, members of a new family of antimicrobial peptides constitutively produced and stored in the haemocytes of penaeid shrimp, display antimicrobial activity against bacteria, and fungi. Here, a DNA sequence encoding the mature Ch-penaeidin peptide was cloned into the pPIC9K vector and transformed into Pichia pastoris. The transformed cells were screened for multi-copy plasmids using increasing concentrations of G418. Positive colonies carrying chromosomal integrations of the Chp gene were identified by phenotype and PCR. When transformed cells were induced with methanol, SDS-PAGE and Western blotting revealed the production of a approximately 6100 Da recombinant CHP (rCHP) expression product. Large scale expression revealed that rCHP was produced at 108 mg/L under optimal conditions in the highest Chp-producing P. pastoris clone. The antimicrobial activities of rCHP were studied by liquid phase analysis, which revealed that rCHP exhibited activities against some Gram-negative and Gram-positive bacteria, but had a relatively low activity against some fungi. Purification of rCHP by cation exchange chromatography and subsequent automated amino acid sequencing revealed the presence of four additional amino acids (YVEF) at the N-terminus that belonged to the cleaved fusion signal peptide; these residues may account for the observed decrease in antifungal activity. Together, these observations indicate that rCHP is an effective antimicrobial peptide that can be successfully produced at high levels in the yeast, and therefore may be a potential antimicrobial candidate for practical use.     

Activation of activin type IB receptor signals in pancreatic β cells leads to defective insulin secretion through the attenuation of ATP-sensitive K channel activity

In studies of gene-ablated mice, activin signaling through activin type IIB receptors (ActRIIB) and Smad2 has been shown to regulate not only pancreatic β cell mass but also insulin secretion. However, it still remains unclear whether gain of function of activin signaling is involved in the modulation of pancreatic β cell mass and insulin secretion. To identify distinct roles of activin signaling in pancreatic β cells, the Cre-loxP system was used to activate signaling through activin type IB receptor (ActRIB) in pancreatic β cells. The resultant mice (pancreatic β cell-specific ActRIB transgenic (Tg) mice; ActRIBCAβTg) exhibited a defect in glucose-stimulated insulin secretion (GSIS) and a progressive impairment of glucose tolerance. Patch-clamp techniques revealed that the activity of ATP-sensitive K⁺ channels (K_ATP channels) was decreased in mutant β cells. These results indicate that an appropriate level of activin signaling may be required for GSIS in pancreatic β cells, and that activin signaling involves modulation of K_ATP channel activity.     

Clinico-molecular study of dedifferentiation in well-differentiated liposarcoma

Well-differentiated liposarcoma (WD) acquires fully malignant potential when the histological progression named dedifferentiation occurs. This progression is supposed to occur in a time-dependent manner but this is still a debated issue. Clinically, the prediction of dedifferentiation for WD is very important from the therapeutic point of view. To identify genes that are predictive of dedifferentiation and to understand the mechanism of dedifferentiation, we investigated clinical information of 50 cases and studied the gene expression profiles of 36 lipomatous tumors using cDNA microarray. The clinical study showed that the dedifferentiation did not always seem to occur in a time-dependent manner. Interestingly, from the gene expression study, unsupervised hierarchical clustering analysis of well-differentiated lesions obtained from dedifferentiated liposarcoma (DD) cases that were indistinguishable from WD pathologically showed a clearly distinct gene expression pattern from WD. Using the pattern-matching program, 1687 genes including 487 known genes were identified, which discriminated WD cases from well-differentiated lipomatous lesions obtained from DD cases. These results suggest that the dedifferentiation may arise from different types of WD that could be distinguished from gene expression profiling but could hardly be classified by the pathological studies.     

Immobilization of immunoglobulin-G-binding domain of Protein A on a gold surface modified with biotin ligase

Protein A from Staphylococcus aureus specifically binds to the Fc region of immunoglobulin G (IgG) and is widely used as a scaffold for the immobilization of IgG antibodies on solid supports. It is known that the oriented immobilization of Protein A on solid supports enhances its antibody-binding capability in comparison with immobilization in a random manner. In the current work, we developed a novel method for the oriented immobilization of the IgG-binding domain of Protein A based on the biotinylation reaction from archaeon Sulfolobus tokodaii. Biotinylation from S. tokodaii has a unique property in that the enzyme, biotin protein ligase (BPL), forms a stable complex with its biotinylated substrate protein, biotin carboxyl carrier protein (BCCP). Here, BCCP was fused to the IgG-binding domain of Protein A, and the resulting fusion protein was immobilized on the BPL-modified gold surface of the sensor chip for quartz crystal microbalance through complexation between BCCP and BPL. The layer of the IgG-binding domain prepared in this way successfully captured the antibody, and the captured antibody retained high antigen-binding capability.     

X-ray studies of water structure in 2 Zn insulin crystal

The water structure of rhombohedral 2 Zn insulin crystal which contains about 280 water molecules and 0.55-0.60 mol citrate molecules per dimer has been studied by X-ray crystallographic refinement with 1.1 A resolution data. Atomic parameters of 83 fully occupied and 258 partially occupied water molecules and 0.3 mol of citrate were obtained. Full matrix least-squares method with isotropic temperature factor was used for the refinement of partially occupied water molecules. The water molecules in this crystal exist in one of the three states: fully occupied water, partially occupied water and water continuum, and a schematic model of water structure in protein crystal was proposed. The flexibility of water molecules is described.     

Sensitive fluorimetric method for the determination of putrescine,spermidine and spermine by high-performance liquid chromatography and its application to human blood

A fast and sensitive method for the determination of putrescine, spermidine and spermine by high-performance liquid chromatography is described. These compounds are converted to their fluorescent dansyl derivatives and are separated by a reversed-phase chromatographic system (Micropak CH-10) with water and acetonitrile as mobile phase. The sensitivity of the method is 30 pmoles.The application of the method to the determination of polyamines in blood is described. It was found that most of the polyamines circulating in blood are localized in the erythrocytes, their content in normal human blood being spermidine 14.1 ± 3.1, and spermine 8.4 ± 2.8 nmoles/ml packed erythrocytes. Putrescine is not present in normal human erythrocytes. The polyamine level in serum is less than 0.1 nmole/ml.The polyamine content of the erythrocytes from patients with malignant neoplasm was significantly elevated.