Photo-controlled self-assembly behavior of novel amphiphilic polymers with rosin-based azobenzene group

Novel ‘bola’ rosin-based photo-responsive amphiphilic polymers PMPn (n=17, 34, 69) were synthesized using polyethyleneglycol (PEG) as a double hydrophilic head and N-azobenzenemaleimidepimaric (AZOMPA) as a hydrophobic tail. The relatively fixed...

Liposomes: Structure, Biomedical Applications, and Stability Parameters With Emphasis on Cholesterol

Liposomes are essentially a subtype of nanoparticles comprising a hydrophobic tail and a hydrophilic head constituting a phospholipid membrane. The spherical or multilayered spherical structures of liposomes are highly rich in lipid contents with numerous criteria for their classification, including structural features, structural parameters, and size, synthesis methods, preparation, and drug loading. Despite various liposomal applications, such as drug, vaccine/gene delivery, biosensors fabrication, diagnosis, and food products applications, their use encounters many limitations due to physico-chemical instability as their stability is vigorously affected by the constituting ingredients wherein cholesterol performs a vital role in the stability of the liposomal membrane. It has well established that cholesterol exerts its impact by controlling fluidity, permeability, membrane strength, elasticity and stiffness, transition temperature (Tm), drug retention, phospholipid packing, and plasma stability. Although the undetermined optimum amount of cholesterol for preparing a stable and controlled release vehicle has been the downside, but researchers are still focused on cholesterol as a promising material for the stability of liposomes necessitating explanation for the stability promotion of liposomes. Herein, the prior art pertaining to the liposomal appliances, especially for drug delivery in cancer therapy, and their stability emphasizing the roles of cholesterol.

Cyanochelins, an overlooked class of widely distributed cyanobacterial siderophores, discovered by silent gene cluster awakening.

Cyanobacteria require iron for growth and often inhabit iron-limited habitats, yet only a few siderophores are known to be produced by them. We report that cyanobacterial genomes frequently encode PKS/NRPS biosynthetic pathways for synthesis of lipopeptides featuring β -hydroxyaspartate ( β -OH-Asp), a residue known to be involved in iron chelation. Iron starvation triggered the synthesis of β -OH-Asp lipopeptides in the cyanobacteria Rivularia sp. PCC 7116, Leptolyngbya sp. NIES-3755 and Rubidibacter lacunae KORDI 51-2. The induced compounds were confirmed to bind iron by mass spectrometry and were capable of Fe 3+ to Fe 2+ photoreduction accompanied by their cleavage, when exposed to sunlight. The siderophore from Rivularia , named cyanochelin A, was structurally characterized by MS and NMR and contains a hydrophobic tail bound to phenolate and oxazole moieties followed by five amino acids including two modified aspartate residues for iron chelation. Phylogenomic analysis revealed twenty-six additional cyanochelin-like gene clusters across a broad range of cyanobacterial lineages. Our data suggests that cyanochelins and related compounds are widespread, β -OH-Asp-featuring cyanobacterial siderophores produced by phylogenetically distant species upon iron starvation. Production of photolabile siderophores by phototrophic cyanobacteria raises questions to what extent the compounds facilitate iron monopolization by the producer or provide Fe 2+ for the whole microbial community via photoreduction. Significance: All living organisms depend on iron as an essential cofactor for indispensable enzymes. However, the sources of bioavailable iron are often limited. To face this problem, microorganisms synthesize low molecular weight metabolites capable of iron scavenging - the siderophores. Although cyanobacteria inhabit the majority of the Earth's ecosystems, their repertoire of known siderophores is remarkably poor. Their genomes are known to harbour a rich variety of gene clusters with unknown function. Here we report the awakening of a widely distributed class of silent gene clusters by iron starvation, yielding cyanochelins, β -hydroxy aspartate lipopeptides involved in iron acquisition. Our results expand the limited arsenal of known cyanobacterial siderophores and propose products with ecological function to a number of previously silent gene clusters.

Neutron reflectometry and NMR spectroscopy of full-length Bcl-2 protein reveal its membrane localization and conformation

B-cell lymphoma 2 (Bcl-2) proteins are the main regulators of mitochondrial apoptosis. Anti-apoptotic Bcl-2 proteins possess a hydrophobic tail-anchor enabling them to translocate to their target membrane and to shift into an active conformation where they inhibit pro-apoptotic Bcl-2 proteins to ensure cell survival. To address the unknown molecular basis of their cell-protecting functionality, we used intact human Bcl-2 protein natively residing at the mitochondrial outer membrane and applied neutron reflectometry and NMR spectroscopy. Here we show that the active full-length protein is entirely buried into its target membrane except for the regulatory flexible loop domain (FLD), which stretches into the aqueous exterior. The membrane location of Bcl-2 and its conformational state seems to be important for its cell-protecting activity, often infamously upregulated in cancers. Most likely, this situation enables the Bcl-2 protein to sequester pro-apoptotic Bcl-2 proteins at the membrane level while sensing cytosolic regulative signals via its FLD region.

Cationic Single-Chained Surfactants with a Functional Group at the End of the Hydrophobic Tail DNA Compacting Efficiency

The interaction between calf-thymus DNA, ctDNA, and various single-chained surfactants with different functional groups at the end of hydrophobic tail was studied with the goal of investigating the influence of the functional group nature on surfactant DNA compacting efficiency. The surfactants investigated were dodecyltriethylammonium bromide (DTEABr), triethyl(1-phenoxydodecyl)ammonium bromide (12PhBr), triethyl(2-naphthoxydodecyl)ammonium bromide (12NBr) and 11-(isonicotinoyloxy)-N,N,N-triethyl-1-undecanaminium bromide (11PyBr). Results made evident that the surfactants’ tendencies to self-aggregation is the key factor determining their efficiency to compact the nucleic acid. Subsequently, DOPE/12NBr/pEGFP-C1 lipoplexes, with different cationic surfactant molar fractions (α) and mass ratios (L/D), were prepared and characterized. DOPE is a zwitterionic phospholipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine, and the plasmid pEGFP-C1 carries a GFP coding sequence with the necessary regulatory elements for constitutive expression of the gene in human cells. 12NBr was chosen because it was the most efficient DNA compacting agent among the surfactants investigated. Finally, the cytotoxicity and transfection efficiency (TE) of DOPE/12NBr/pDNA lipoplexes, with different compositions, were investigated.

Antimicrobial activity and cytotoxicity of transition metal carboxylates derived from agaric acid

Carboxylato-type transition metal complexes with agaric acid, a bioactive natural compound derived from citric acid, were prepared, and tested in vitro for their antimicrobial activity and cytotoxicity. The products as well as agaric acid itself are amphiphilic compounds containing a hydrophilic head (citric acid moiety) and a hydrophobic tail (non-polar alkyl chain). The putative composition of the carboxylates was assigned on grounds of elemental analysis, infrared (IR) and high-resolution mass spectra (HR-MS), as well as in analogy with known complexes containing the citrate moiety. The metal carboxylates showed interesting activity in several microbial strains, especially against S. aureus (vanadium complex; MIC = 0.05 mg/ml). They were also tested for their cytotoxic activity in hepatocytes, the highest activity having been found in the copper(II) and manganese(II) complexes. Further research based on these preliminary results is needed in order to evaluate the influence of parameters like stability of the metal complexes in solution on the bioactivity of the complexes.

Organic Semiconductors with Benzoic Acid Based Additives for Solution-Processed Thin Film Transistors

Background: although solution-processed small molecular organic semiconductors have attracted great attention for organic electronic applications,the intrinsic crystal misorientation of the organic semiconductorsstill remains as a challenging issue. Objective: two benzoic acid-based additives, i.e. 4-propylbenzoic acid (RBA) and 4-octylbenzoic acid (OBA), were employed to regulate the crystal growth and charge transport of organic semiconductors. Methods: RBA and OBA were mixed with a π-conjugated organic semiconductor 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene), respectively. Organic thin film transistors (OTFTs) with different bottom-gate, top-contact and bottom-gate, bottom-contact configurations were fabricated to investigate charge transport. Results: RBA and OBA share a similar benzoic acid structure with the same hydrophilic head but differ in the length of hydrophobic tail. The benzoic acid-based additive forms a stratified self-assembled interfacial layer and maneuvers nucleation seed distribution via synergetic interactions with the silanol groups on silicon dioxide and with the bulky side chains of the semiconductor. The TIPS pentacene film with OBA additive exhibited a 10-fold reduction in misorientation angle, as compared to the counterpart with RBA. Conclusion: Distinct thin film morphology in terms of crystal alignment and grain width was observed and correlated to the hydrophobic tail length. In particular,OTFTs incorporating the TIPS pentacene/benzoic acid mixture as the active layer showed a mobility of up to 0.15 cm2/Vs.

Propensity, free energy contributions and conformation of primary n-alcohols at a water surface

The transition of primary alcohol molecules from bulk water to the surface is driven by entropy, increasing linearly with length of the hydrophobic tail. The enthalpy of surface adsorption is nearly invariant with increasing length of the molecule.