Hydrophobic Amide Research Articles

Facile fabrication of magnetite nanoparticles with new hydrophobic amides and their application in oil spill remediation.

In this study, inexpensive magnetite nanoparticles (Fe3O4) were prepared and applied to oil spill remediation. To do so, two novel hydrophobic amides, HADN and HATN, were prepared and applied to Fe3O4 surface modification, producing HAN-Fe3O4 and HAT-Fe3O4, respectively. The efficiency of HAN-Fe3O4 and HAT-Fe3O4 for oil spill remediation (EOSR) was investigated using different HAN-Fe3O4 and HAT-Fe3O4 weights and at various contact times. The data indicated that the EOSR increased with increased HAN-Fe3O4 and HAT-Fe3O4 weights, as their EOSR reached 100% and 89%, respectively, using 100 mg. The results also revealed that the optimum time for HAN-Fe3O4 and HAT-Fe3O4 (50 mg) to achieve the highest EOSR is 8 min, as their EOSR reached 98% and 84%, respectively, at this time. In addition, HAN-Fe3O4 exhibited higher EOSR than HAT-Fe3O4, which could be linked to the presence of an aromatic ring in HADN that is used for surface modification of Fe3O4, making them more compatible with crude oil components.

Synthetic Sansanmycin Analogues as Potent Mycobacterium tuberculosis Translocase I Inhibitors.

Herein, we report the design and synthesis of inhibitors of Mycobacterium tuberculosis (Mtb) phospho-MurNAc-pentapeptide translocase I (MurX), the first membrane-associated step of peptidoglycan synthesis, leveraging the privileged structure of the sansanmycin family of uridylpeptide natural products. A number of analogues bearing hydrophobic amide modifications to the pseudo-peptidic end of the natural product scaffold were generated that exhibited nanomolar inhibitory activity against Mtb MurX and potent activity against Mtb in vitro. We show that a lead analogue bearing an appended neopentylamide moiety possesses rapid antimycobacterial effects with a profile similar to the frontline tuberculosis drug isoniazid. This molecule was also capable of inhibiting Mtb growth in macrophages where mycobacteria reside in vivo and reduced mycobacterial burden in an in vivo zebrafish model of tuberculosis.

Impact of Chirality and Position of Lysine Conjugation in Triplex-Forming Peptide Nucleic Acids.

Conjugation with cationic lysine residues improves the biophysical and biological properties of peptide nucleic acids (PNAs). A single lysine is routinely used to improve the solubility and prevent aggregation of the neutral and hydrophobic amide backbone of PNA. Literature precedents include the attachment of lysine at either the N- or the C-terminus. Moreover, conjugation with short lysine peptides (four to eight residues) improves the cellular uptake of PNA akin to more complex cell-penetrating peptides. Herein, we report a systematic study of the effect of lysine location (N- vs C-terminus) and chirality (d- vs l-) on triple-helical binding of PNA to double-stranded RNA and DNA (dsRNA and dsDNA). The results confirmed our earlier findings that conjugation with lysine significantly increased the stability of PNA-dsRNA and PNA-dsDNA triplexes and that PNA affinity for dsRNA was about an order of magnitude higher than for the same sequence of dsDNA. In contrast, conjugation of PNA with noncharged amino acids decreased the affinity of PNA. Surprisingly, neither the location nor the chirality of lysine had significant impact on PNA affinity for either dsRNA or dsDNA. The results are consistent with the lack of chiral preorganization of single-stranded PNAs, even after conjugation with four d- or l-amino acids. Instead, the positive charge of lysine appears to be the main driving force behind the increased affinity.

Solvent-Tolerant Acyltransferase from Bacillus sp. APB-6: Purification and Characterization.

Amidase from Bacillus sp. APB-6 with very good acyltransferaseactivity was purified to homogeneity with a purification fold of 3.68 and 53.20% enzyme yield. The purified protein's subunitmolecular mass was determined approximately 42kDa. Hyperactivity of the enzyme was observed at pH 7.5 (150mM, potassium-phosphate buffer) and 50°C of incubation. An enhancement in activity up to 42% was recorded with ethylenediaminetetraacetic acid and dithiothreitol. The kinetic parameter K m values for substrates: acetamide and hydroxylamine-hydrochloride were 73.0 and 153mM, respectively. Further, the V max for acyltransferase activity was 1667 U/mg of protein and the K i for acetamide was calculated as 37.0mM. The enzyme showed tolerance to various organic solvents (10%, v/v) and worked well in the biphasic reaction medium. The acyltransferase activity in presence of solvents i.e. biphasic medium may prove highly favorable for the transformation of hydrophobic amides, which otherwise is not possible in simple aqueous phase.

Amides as a model system of low molar mass algal organic matter. Influence on the adsorption of p-nitrophenol on activated carbon

In this study, the adsorption equilibrium and diffusivity parameters of p-nitrophenol were estimated for water containing different concentrations of secondary amides. Commercial powdered activated carbon was used as an adsorbent. The external mass transfer coefficient (kf), the surface diffusion coefficient (Ds) and the standard free Gibbs energy were calculated for p-nitrophenol in the presence of different secondary amide concentrations. The analysis established that there are correlations between structural parameters of amides, on the one hand, and diffusion and thermodynamic parameters for p-nitrophenol adsorption process, on the other. It was noticed that voluminous hydrophobic amides decreased the adsorption capacity of p-nitrophenol on activated carbon. On the basis of the results obtained for external mass transfer coefficients, it is assumed that amides cause the reduction of adsorption capacity of p-nitrophenol onto activated carbon by concentrating at the solid/liquid interface.

The effect of regioisomerism on the coordination chemistry and CEST properties of lanthanide(III) NB-DOTA-tetraamide chelates

Chemical exchange saturation transfer (CEST) offers many advantages as a method of generating contrast in magnetic resonance images. However, many of the exogenous agents currently under investigation suffer from detection limits that are still somewhat short of what can be achieved with more traditional Gd(3+) agents. To remedy this limitation we have undertaken an investigation of Ln(3+) DOTA-tetraamide chelates (where DOTA is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) that have unusually rigid ligand structures: the nitrobenzyl derivatives of DOTA-tetraamides with (2-phenylethyl)amide substituents. In this report we examine the effect of incorporating hydrophobic amide substituents on water exchange and CEST. The ligand systems chosen afforded a total of three CEST-active isomeric square antiprismatic chelates; each of these chelates was found to have different water exchange and CEST characteristics. The position of a nitrobenzyl substituent on the macrocyclic ring strongly influenced the way in which the chelate and Ln(3+) coordination cage distorted. These differential distortions were found to affect the rate of water proton exchange in the chelates. But, by far the greatest effect arose from altering the position of the hydrophobic amide substituent, which, when forced upwards around the water binding site, caused a substantial reduction in the rate of water proton exchange. Such slow water proton exchange afforded a chelate that was 4.5 times more effective as a CEST agent than its isomeric counterparts in dry acetonitrile and at low temperatures and very low presaturation powers.

Hydrophobic vs. hydrophilic ionic liquid separations strategies in support of continuous pharmaceutical manufacturing

Taking advantage of the dramatically different solvent properties of hydrophilic ionic liquids (ILs) when dry vs. when wet allows unique separations strategies compared to the use of hydrophobic ionic liquids. This is demonstrated here by comparing the separation of a water insoluble amide intermediate for aliskiren from its reactants, a water insoluble lactone, water soluble 3-amino-2,2-dimethylpropanamide, and the water soluble promoter 2-ethylhexanoic acid, using the hydrophobic ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][NTf2]) and the hydrophilic ionic liquid 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]). Both the water soluble [C2mim][OAc], when dry, and water insoluble [C2mim][NTf2] can dissolve the highly hydrophobic and hydrophilic compounds simultaneously, but the two ILs require different strategies to separate the mixtures of these compounds. Using the hydrophobic [C2mim][NTf2], the hydrophobic compounds can be separated from the hydrophilic reactants by extraction and precipitation with water, however, the hydrophobic IL is more difficult to completely remove after the separations. In [C2mim][OAc], the most hydrophobic starting material can be extracted from the IL phase into ethyl acetate, and then water can be added to precipitate the hydrophobic amide product while at the same time removing the IL from the pharmaceuticals.

Water-DMF-L-α-alanine and water-carbamide-L-α-alanine systems. Thermodynamic properties, solvation, and interspecies interactions at 273–333 K

Thermal effects of dissolution of L-α-alanine in water-N,N-dimethylformamide mixtures (0–0.1 molar parts of DMF) at 283–318 K were measured calorimetrically. Standard enthalpies and heat capacities of dissolution of the amino acid and also thermal variations in entropies and free energies were calculated. The comparison with previously obtained data on the thermodynamics of dissolution of L-α-alamine in the carbamide water solution was performed. Temperature variations in the reduced Gibbs energy in the course of dissolution of L-α-alanine in water-DMF and water-carbamide mixtures have negative values originating from the prevalence of the entropy component. At the increase in temperature both mixtures become less structured. The interaction of L-α-alanine with hydrophilic and hydrophobic amides differs fundamentally: In the first case it is enthalpy-attractive and does not depend on temperature, while in the second case it is repulsive and decreases with the increase in temperature.

Designer multi-functional comb-polymers for surface engineering of quantum dots on the nanoscale

Synthesis, characterization and cell-biomarker applications for a novel series of comb-copolymers featuring hydrophobic amide side groups, carboxylates and other functionalities such as polymerizable side chains and PEG oligomers are reported. When used as polymer ligand shell for trioctylphosphine oxide (TOPO) coated quantum dots (QDs) these copolymers effectively solubilise CdSe/ZnS QDs in water. A systematic study was carried out to find the relation between the molecular structure of the copolymers, their ability to coat the QDs, and to suspend the nanocrystals in water. To demonstrate potential applications, highly luminescent QD/polymer assemblies were internalized into living and fixed cells.

Photostability of hydrophobic amides of pyridinecarboxylic acid as copper extractants from chloride media

The photostability of N-alkyl and N,N-dialkylpyridine-3-carboxamide, and N-alkyl and N,N-dialkylpyridine-2-carboxamide, and their copper complexes were studied. The obtained results indicated the influence of light (UV and vis) on the stability of pyridinecarboxamides. The degree of photodegradation depended on the type of solvent, the presence of water, hydrochloric acid or air in the solution. Also, the structure of compounds (the number and position of the amides group, structure of the amides carbon chain) influenced amides photostability. Products of photofragmentation of amides groups and photosubstitution at the pyridine ring were identified. Influence of ions of copper(II) and chloride during the photodegradation of copper complexes with pyridinecarboxamide was analyzed.

Role of the Glycopeptide Framework in the Antibacterial Activity of Hydrophobic Derivatives of Glycopeptide Antibiotics

The antibacterial properties of glycopeptide antibiotics are based on their interaction with the d-Ala-d-Ala containing pentapeptide of bacterial peptidoglycan. The hydrophobic amides of vancomycin (1), teicoplanin (2), teicoplanin aglycon (3), and eremomycin (4) were compared with similar amides of minimally or low active des-(N-methyl-d-leucyl)eremomycin (5), eremomycin aglycon (6), des-(N-methyl-d-leucyl)eremomycin aglycon (7), and a teicoplanin degradation product TB-TPA (8). All hydrophobic amides of 1, 3, 4, and 6 were almost equally active against glycopeptide-resistant enterococci (GRE) [minimum inhibitory concentrations (MIC) <or= 4 microg/mL] and had better activity against Gram-positive strains sensitive to glycopeptides than against GRE. Extensive degradation of the glycopeptide framework in amides of 7 and 8 led to a decrease of anti-GRE activity (MIC = 16-64 microg/mL), and for these derivatives MIC values for bacterial strains sensitive and resistant to glycopeptides were very close. These results suggest that in sensitive bacteria two mechanisms of action are operating for the hydrophobic derivatives of glycopeptide antibiotics with the nondamaged peptide core-interaction with the d-Ala-d-Ala moiety and the inhibition of bacterial membrane bound enzymatic reactions, whereas for GRE lacking the d-Ala-d-Ala fragment, only the second mechanism is operating. It appears that a minimal glycopeptide core is required for activity, and that more extensive degradation results in a serious decrease of antibacterial activity.

Poly(itaconic acid)-modified chitosan coatings for mitigating corrosion of aluminum substrates

To make a water-insoluble chitosan (CS) biopolymer, the synthetic poly(itaconic acid) (PIA) polymer was added to graft it onto the liner CS chains and to crosslink between the CS chains. The grafting and crosslinking reactions were generated by a strong chemical affinity between the NH 2 groups in the CS and the COOH groups in the PIA, leading to the formation of amide bonds. When this polymer was applied as environmentally benign water-based coatings to an aluminum (Al) substrate by a simple dip-withdrawing method, the following three factors played an essential role in mitigating the rate of corrosion of the Al: first was the polymer’s conformation containing hydrophobic amide bonds, together with a minimal amount of hydrophilic unreacted COOH in PIA and NH 2 in CS; second was the lesser susceptibility of the coating films to moisture due to the enhanced degree of grafting and crosslinking; and third was the interactions at the interfaces between the grafted CS and the Al substrate, developing the formation of the –COO–Al linkage. The PIA-grafted and -crosslinked CS polymer coating films generated from the proper proportions of PIA to CS included all these factors and displayed low ionic conductivity, thereby imparting a salt-spray resistance of 694 h for coated Al panels.