Collagen-like peptides and peptide–polymer conjugates in the design of assembled materials

Collagen is the most abundant protein in mammals, and there has been long-standing interest in understanding and controlling collagen assembly in the design of new materials. Collagen-like peptides (CLPs), also known as collagen-mimetic peptides (CMPs) or collagen-related peptides (CRPs), have thus been widely used to elucidate collagen triple helix structure as well as to produce higher-order structures that mimic natural collagen fibers. This mini-review provides an overview of recent progress on these topics, in three broad topical areas. The first focuses on reported developments in deciphering the chemical basis for collagen triple helix stabilization, which we review not with the intent of describing the basic structure and biological function of collagen, but to summarize different pathways for designing collagen-like peptides with high thermostability. Various approaches for producing higher-order structures via CLP self-assembly, via various types of intermolecular interaction, are then discussed. Finally, recent developments in a new area, the production of polymer–CLP bioconjugates, are summarized. Biological applications of collagen contained hydrogels are also included in this section. The topics may serve as a guide for the design of collagen-like peptides and their bioconjugates for targeted application in the biomedical arena.     

Design of peptide–dendrimer conjugates with tumor homing and antitumor effects

Development of drug delivery systems for cancer therapy is a crucial issue. Previously, some peptides were designed as tumor homing cell-penetrating peptides with antitumor activities. In this study, dual function dendrimers with tumor targeting activities and antitumor effects were designed using the tumor targeting CPP44 peptide for acute myelogenous leukemia (AML) and the antitumor p16^INK4a peptide. Two types of peptide–dendrimer conjugates were synthesized. One was a CPP44-linked p16^INK4a peptide-conjugated dendrimer (tandem linked dendrimer) and the other was a dendrimer conjugated with separate CPP44 and p16^INK4a peptides (parallel linked dendrimer). In addition, a peptide cathepsin B substrate was linked to the antitumor p16^INK4a peptide to release it from the carriers. These peptide–dendrimer conjugates produced more effective antitumor effects than a CPP44-linked p16^INK4a peptide. The parallel linked dendrimer showed less association with AML cells than the tandem linked dendrimer, but had greater antitumor effects. This suggested that both cellular uptake and antitumor peptide cleavage affected the antitumor activities of dual functional peptide-conjugated dendrimers.     

Synthesis and evaluation of peptide–fentanyl analogue conjugates as dual µ/δ-opioid receptor agonists for the treatment of pain

Novel peptide-fentanyl analogue conjugates were synthesized by the covalent coupling of carfentanyl derivatives to the C-terminus or N-terminus of the conformationally constrained dermorphin tetrapeptide BVD03 via a chemical linker. The carfentanyl-related analogues displayed distinct binding and functional activities at µ/δ opioid receptors (MOR/DOR) and antinociceptive effects when conjugated to the peptide. The most potent compound, SW-LJ-11, displayed mixed MOR/DOR agonist properties in the low nanomolar range and significant analgesic efficacy in vivo in four classic mouse models of pain. Interestingly, SW-LJ-11 did not exhibit any physical dependence or respiratory depression, in contrast to an equipotent analgesic dose of morphine or BVD03, indicating that the use of opioid peptide–fentanyl analogue conjugates as dual MOR/DOR agonists may be a promising strategy for obtaining safer opioids.     

Correlations between the number of thiophene units and the photovoltaic behavior of fluorene–oligothiophene copolymers

The photophysical and photovoltaic properties of three alternated fluorene–thiophene copolymers were studied. With similar structure the copolymers differed by the numbers of thiophene units linked to each fluorene group:one, two and three. The electronic properties were analyzed through mobility measurements and the overall properties pointed out to the one containing the three rings as the best material, as anticipated, due to the larger number of thiophene units. However, after thermal annealing the polymer containing two thiophene rings presented the best photovoltaic efficiency, seven fold greater than the pristine material. The morphology, studied by atomic force microscopy, revealed to be one of the key factors for the performance of the materials as solar cells.     

DFT study of the electronic and charge transfer properties of perfluoroarene–thiophene oligomers

The ground state structures of 5,5″-diperfluorophenyl-2,2′:5′,2″:5″,2‴-quaterthiophene (1), 5,5′-bis{1-[4-(thien-2-yl)perfluorophenyl]}-2,2′-dithiophene (2), 4,4′-bis[5-(2,2′-dithiophenyl)]-perfluorobiphenyl (3), 5,5″-diperfluorophenyl-2,2′:5′,2″-tertthiophene (4), 5,5′-diperfluorophenyl-2,2′-dihiophene (5), and 5,5-diperfluorophenylthiophene (6) have been optimized at the B3LYP/6-31G(d), B3LYP/6-31G(d,p), PBE0/6-31G(d), and PBE0/6-31G(d,p) level of theories. The B3LYP/6-31+G(d) and PBE0/6-31+G(d) level of theories have been applied to investigate the absorption spectra. The PBE0 functional is good to predict the C–S bond lengths while the C–F bond lengths are good envisaged with B3LYP functional. The increment of thiophene rings between two perfluoroarene rings leads to red shift in absorption spectra. The electron affinities are energetically destabilized while energetic stabilization of the radical-cation increases by decreasing the thiophene rings from four to one. The perfluoroarene rings leads to enhance the electron injection.     

The synthesis and bioevaluation of the dicyclic arene-homospermidine conjugates

Four novel dicyelic arene-homospermidine conjugates (6a-d) were synthesized and evaluated for cytotoxicity in L1210,α- difluoromethylomithine (DFMO) treated L1210,melanoma B16,spermidine (SPD) treated B16,and Hela cells.In the DFMO- treated L1210 experiments,6a-d were more sensitive to DFMO than naphthalene-homospermidine (6e),suggesting that 6a-d can utilize the polyamine transporter (PAT) to enter the cells as well as 6e.The diminished cytotoxicity in the SPD/B16 experiments also supported this conclusion.In summary,the homospermidine is an efficacious vector to ferry dicyclic arches into cells via PAT.     

DSC study of phase transition of anhydrous phospholipid DHPC and influence of water content

The phase transition behavior of 1,2-di-n-heptadecanoyl phosphatidylcholme (DHPC)with and without water has been studied by use of differential scanning calorimetry It was found by experiment that the glass transition occurred at first during the first heating of a sample of DHPC without water and then the sample underwent melting as an ordinary crystal.Therefore the sample of DHPC without water was a glassy crystal However,the DHPC sample crystallizing from melt was an ordinary crystal From the relationship between the total melting enthalpy Qf of freezable water and the water content h,it was concluded that the water contained in the DHPC samples might exist in three states recognizable thermodynamically.The water in the first state was an unfreezable water It was the water bound directly with the head groups of the phospholipid,i.e.the primary hydration water Every head group might bind seven such molecules of water.The water in the second state was the secondary hydration water,us melt ing point was     

Catalytic properties of nickel–yttrium mixed oxides and the influence of ionizing radiation

Some physico-chemical and catalytic properties of NiO–Y₂O₃ cataysts containing various amounts of components in the range 0–100 wt% of one component have been studied before and after 1 MGy gamma or accelerated electron irradiation in air or in water using the hydrogen peroxide decomposition as a test reaction. Both kinds of irradiation led only to a change in surface oxidative ability but did not lead to modification of the catalytic activity of the catalysts. The reduction of the catalysts led to a creation of new kind of catalytic sites.     

Synthesis,antioxidant and anticancer screenings of berberine–indole conjugates

Research on Chemical Intermediates - A variety of heterocyclic nitrogen cores in the form of indole moieties were linked to the natural isoquinoline alkaloid molecule berberine to achieve...     

Sequence and linker dependent chiral dimerization of DNA–porphyrin conjugates

Circular dichroism (CD), UV–vis absorption, fluorescence, and resonance light scattering (RLS) spectroscopies were used to elucidate the role of the DNA sequence, linkers between DNA and porphyrin, and metal in the porphyrin coordination center on the self-assembly of DNA–porphyrin conjugates. A series of eight non-self-complementary DNA–porphyrin conjugates have been synthesized with zinc and free-base porphyrins covalently attached to the short ODNs (A₈ or T₈) via amide or phosphate linker. A small structural modification (e.g., amide linker replaced by the phosphate linker) showed a dramatic effect on the aggregation properties of DNA–porphyrin conjugates and greatly altered their spectroscopic properties. At low ionic strength, porphyrin aggregation was not observed for any conjugate. An increase in the ionic strength caused two out of eight conjugates to form chiral porphyrin dimers.     

Preparation and characterization of nanocomposite ZnO–Ag thin film containing nano-sized Ag particles: influence of preheating,annealing temperature and silver content on characteristics

Nanocomposite ZnO–Ag thin film containing nano-sized Ag particles have been grown on glass substrate by spin-coating technique using zinc acetate dihydrate as starting precursor in 2-propanol as solvent and monoethanolamine as stabilizer. Silver nanoparticles were added in the ZnO sol using silver nitrate dissolved in ethanol-acetonitrile. Their structural, electrical, crystalline size and optical properties were investigated as a function of preheating, annealing temperature and silver content. The results indicated that the crystalline phase was increased with increase of annealing temperature up to 550 °C at optimum preheating temperature of 275 °C. Thermal gravimetric differential thermal analysis results indicated that the decomposition of pure ZnO and nanocomposite ZnO–Ag precursors occurred at 225 and 234 °C, respectively with formation of ZnO wurtzite crystals. The scanning electron microscopy and atomic force microscopy revealed that the surface structure (the porosity and grain size) of the ZnO–Ag thin film (the film thickness is about 379 nm) was changed compared to pure ZnO thin film. The result of transmission electron microscopy showed that Ag particles were about 5 nm and ZnO particles 58 nm with uniform silver nanoclusters. Optical absorption results indicated that optical absorption of ZnO–Ag thin films decreased with increase of annealing temperature. Nanocomposite ZnO–Ag thin films with [Ag] = 0.068 M and [Ag] = 0.110 M showed an intense absorption band, whose maximum signals appear at 430 nm which is not present in pure ZnO thin films. The result of X-ray photoelectron spectroscopy revealed that the binding energy of Ag 3d_5/2 for ZnO–Ag shifts remarkably to the lower binding energy compared to the pure metallic Ag due to the interaction between Ag and ZnO.     

Ferrocenylmethylation of estrone and estradiol: Structure,electrochemistry, and antiproliferative activity of new ferrocene–steroid conjugates

Conjugates of ferrocene with steroidal estrogens as selective antiproliferative agents against hormone-dependent breast cancer cells are believed to be limited by the inherent estrogenicity of the conjugates. Motivated by a significant cytotoxicity of the ester of ferrocenecarboxylic acid and the phenolic group of estradiol toward such a cell line, we decided to explore other a -ring-tethered ferrocene–estra-1,3,5(10)-triene conjugates; in this study, ferrocenylmethylation of estradiol and estrone with (ferrocenylmethyl)trimethylammonium iodide in the presence of potassium carbonate yielded five new compounds ( 1 – 5 ). In dimethylformamide, only O-alkylated products formed ( 1 and 3 ), while a mixture of O- and C-alkylated products was obtained when methanol was used ( 2 , 4 , and 5 in addition to 1 and 3 ). All compounds were characterized using 1D and 2D NMR, IR, UV–Vis, and high-resolution mass spectrometry. Two of the conjugates, a 3-O- and a 4-C-alkylated derivative of estrone ( 3 and 4 , respectively), were also analyzed using single-crystal X-ray diffraction. A cyclic voltammetric investigation of the electrochemical properties of 1 – 5 was performed. While some of the compounds were shown to have a slight-to-moderate antiproliferative activity against at least one of the six tested human tumor cell lines and were nontoxic to (the noncancerous) fetal human fibroblasts, compound 2 (4-(ferrocenylmethyl)estra-1,3,5(10)-triene-3,17β-diol) with an IC₅₀ value of 0.34 μM was found to be more active against the hormone-dependent breast cancer cell line MCF-7 than doxorubicin. These results suggest that a -ring substitution of steroidal estrogens is a plausible strategy for preparing other ferrocene–steroid conjugates acting against tumor cells.     

Expanding the Toolbox of Metal–Phenolic Networks via Enzyme-Mediated Assembly

Functional coatings are of considerable interest because of their fundamental implications for interfacial assembly and promise for numerous applications. Universally adherent materials have recently emerged as versatile functional coatings; however, such coatings are generally limited to catechol, (ortho-diphenol)-containing molecules, as building blocks. Here, we report a facile, biofriendly enzyme-mediated strategy for assembling a wide range of molecules (e.g., 14 representative molecules in this study) that do not natively have catechol moieties, including small molecules, peptides, and proteins, on various surfaces, while preserving the molecule's inherent function, such as catalysis (≈80 % retention of enzymatic activity for trypsin). Assembly is achieved by in situ conversion of monophenols into catechols via tyrosinase, where films form on surfaces via covalent and coordination cross-linking. The resulting coatings are robust, functional (e.g., in protective coatings, biological imaging, and enzymatic catalysis), and versatile for diverse secondary surface-confined reactions (e.g., biomineralization, metal ion chelation, and N-hydroxysuccinimide conjugation).     

Amberlyst-15 catalyzed synthesis of novel thiophene–pyrazoline derivatives: spectral and crystallographic characterization and anti-inflammatory and antimicrobial evaluation

Increasing instances of antimicrobial drug resistance and Inflammation-mediated disorders requires the design and synthesis of new small-molecules with higher affinity and specificity for their potential targets to serve as antibiotics or anti-inflammatory drugs, respectively. The current study presents the synthesis of a series of chalcones, 3(a–h) by the reaction of 3-methylthiophene-2-carbaldehyde, 1 and acetophenones, 2(a–h) by Claisen–Schmidt approach. The chalcones were efficiently transformed into thienyl-pyrazolines, 5(a–h) by their reaction with thiosemicarbazide hydrochloride, 4 in the presence of Amberlyst-15 as a catalyst in acetonitrile at room temperature. Alternatively, the compounds 5(a–h) were prepared by conventional method using acetic acid (40%) medium. Structures were characterized by spectral and single crystal X-ray diffraction studies. Preliminary assessment of the anti-inflammatory properties of the compounds showed that, amongst the series, compounds 5b and 5c have excellent anti-inflammatory activities. Further, compound 5c showed excellent activity against Escherichia coli (MIC, 15 µg/mL), Bacillus subtilis (MIC, 20 µg/mL), Aspergillus niger (MIC, 20 µg/mL), and Aspergillus flavus (MIC 15 µg/mL), respectively. Compounds 5a and 5b were also found to be active against the tested microorganisms.     

Sol–gel reactions of titanium alkoxides and water: influence of pH and alkoxy group on cluster formation and properties of the resulting products

In this work the effect of pH and the titanium precursor on the cluster and particle formation during titanium alkoxide based sol–gel processes was investigated using electrospray ionization mass spectrometry (ESI-MS) and dynamic light scattering (DLS). The influence of pH and the titanium precursor on the particle size, morphology, crystallinity and chemical composition of the resulting particles were investigated using differentiel scanning calometry (DSC), X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR), BET-adsorption isotherms and high resolution transmission electron microscopy (HR-TEM). ESI-MS investigation of the titanium clusters present during the nucleation and growth period showed that the number of titanium atoms in the clusters varied dependent on the alkoxide used. Moreover, it was found that the titanium clusters formed using titanium tetraethoxide (TTE) were smaller than the clusters formed by titanium tetraisopropoxide (TTIP) and titanium tetrabutoxide (TTB) under similar conditions. pH was not found to influence the nature of the titanium clusters present in the sol–gel solution. HR-TEM investigation of the TiO₂ particles prepared at pH 7 and 10 showed that the primary particle size of the particles was around 3 nm. However, it was found that these primary particles aggregated to form larger secondary particles in the size order of 300–500 nm range. At pH 3 the particles grew significantly during the drying process due to destabilization of the colloidal solution leading to the formation of a gel. The highest specific surface area was found for particles synthesized under neutral or alkaline conditions based on TTIP. XRD analysis of the TiO₂ particles showed that the particles synthesized at 25 °C were amorphous. First after heating the samples to above 300 °C the formation of anatase were observed.     

Application of nucleic acid–lipid conjugates for the programmable organisation of liposomal modules

We present a critical review of recent work related to the assembly of multicompartment liposome clusters using nucleic acids as a specific recognition unit to link liposomal modules. The asymmetry in nucleic acid binding to its non-self complementary strand allows the controlled association of different compartmental modules into composite systems. These biomimetic multicompartment architectures could have future applications in chemical process control, drug delivery and synthetic biology. We assess the different methods of anchoring DNA to lipid membrane surfaces and discuss how lipid and DNA properties can be tuned to control the morphology and properties of liposome superstructures. We consider different methods for chemical communication between the contents of liposomal compartments within these clusters and assess the progress towards making this chemical mixing efficient, switchable and chemically specific. Finally, given the current state of the art, we assess the outlook for future developments towards functional modular networks of liposomes.     

Synthesis and characterization of alternating fluorene–thiophene copolymers bearing ethylene glycol side-chains

Abstract  

New alternating fluorene–thiophene copolymers are introduced bearing polar ethylene glycol-carboxylate functionalities on the thiophene ring to achieve enhanced solubility in polar solvents. Suzuki polycondensation was applied to synthesize a set of three polymers with differing lengths of the ethylene glycol side-chains. The polymers are thermally stable up to temperatures of 300 °C. Solutions of the polymers in CHCl₃ show an absorption maximum at approximately 397 nm and a luminescence maximum of 472 nm in solutions with quantum yield of 30%. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels have been determined to be at −5.7 and −2.6 eV, respectively.