Multiple Amine Groups Research Articles

Concentrations, turnover rates and fluxes of polyamines in coastal waters of the South Atlantic Bight

Polyamines are short-chain aliphatic compounds containing multiple amine groups. They are important components of the cytosol of eukaryotes and are present at mmol L−1 concentrations inside phytoplankton cells, while complex polyamines play a role in biosilica deposition. Concentrations of polyamines measured in seawater are typically in the sub-nmol L−1 range, implying rapid and efficient uptake by osmotrophs, likely bacterioplankton. We measured turnover rates of three polyamines (putrescine, spermidine and spermine) using 3H-labeled compounds and determined their concentrations by HPLC to estimate polyamine contributions to dissolved organic matter and bacterioplankton carbon and nitrogen demand. These measurements were made on transects from the inner shelf to the Gulf Stream across the South Atlantic Bight (SAB) during April and October of 2011 and in salt marsh estuaries on the Georgia coast during August of 2011 and April of 2012. We found that turnover rates of polyamines were similar to those of amino acids (arginine and glutamic acid) measured in the same samples; however, fluxes of polyamines into bacterioplankton were much lower than amino acid fluxes as a result of low ambient concentrations. Turnover rates and fluxes of polyamines decreased from near-shore waters to the shelf-break, following the pattern of chlorophyll a concentration. Polyamine uptake accounted for less than 10 % of bacterial N demand and 5 % of bacterial C demand on average, with a large variation among water masses.

Structure and Properties of Polybenzimidazole/Silica Nanocomposite Electrolyte Membrane: Influence of Organic/Inorganic Interface

Although increased number of reports in recent years on proton exchange membrane (PEM) developed from nanocomposites of polybenzimidazole (PBI) with inorganic fillers brought hope to end the saga of contradiction between proton conductivity and variety of stabilities, such as mechanical, thermal,chemical, etc.; it still remains a prime challenge to develop a highly conducting PEM with superior aforementioned stabilities. In fact the very limited understanding of the interactions especially interfacial interaction between PBI and inorganic filler leads to confusion over the choice of inorganic filler type and their surface functionalities. Taking clue from our earlier study based on poly(4,4'-diphenylether-5,5'-bibenzimidazole) (OPBI)/silica nanocomposites, where silica nanoparticles modified with short chain amine showed interfacial interaction-dependent properties, in this work we explored the possibility of enhanced interfacial interaction and control over the interface by optimizing the chemistry of the silica surface. We functionalized the surface of silica nanoparticles with a longer aliphatic chain having multiple amine groups (named as long chain amine modified silica and abbreviated as LAMS). FTIR and (13)C solid-state NMR provided proof of hydrogen bonding interactions between the amine groups of modifier and those of OPBI. LAMS nanoparticles yielded a more distinguished self-assembly extending all over the OPBI matrix with increasing concentrations. The crystalline nature of these self-assembled clusters was probed by wide-angle X-ray diffraction (WAXD) studies and the morphological features were captured by transmission electron microscope (TEM). We demonstrated the changes in storage modulus and glass transition temperature (Tg) of the membranes, the fundamental parameters that are more sensitive to interfacial structure using temperature dependent dynamic mechanical analysis (DMA). All the nanocomposite membranes displayed enhanced mechanical, thermal and chemical stability than neat OPBI. The lower water uptake and swelling ratio and volume in both acid and water reflected the more hydrophobic characteristic of the nanocomposites. All the nanocomposite membranes showed phosphoric acid (PA) values to be higher than OPBI but the levels showed decreasing trend with increasing silica content; the reason attributed to the interparticle interaction. The self-assembled clusters of LAMS nanoparticles in the matrix created more sites for proton hopping as a result of which the proton conductivity of all the nanocomposites displayed an increasing trend.

Structure of Mycobacterium smegmatis Eis in complex with paromomycin.

The Rv2416c gene of Mycobacterium tuberculosis (Mtb) encodes the enhanced intracellular survival (Eis) protein that enhances intracellular survival of the pathogen in host macrophages during infection. The Mtb Eis protein is released into the cytoplasm of the phagocyte during intracellular infection and modulates the host immune response. It also contributes to drug resistance by acetylating multiple amine groups of aminoglycosides. Interestingly, the nonpathogenic M. smegmatis (Msm) contains a homologous eis gene (MSMEG_3513). The overall structures of Mtb Eis and Msm Eis are highly similar to each other, reflecting the high level (58%) of amino-acid sequence identity between them. Both Mtb Eis and Msm Eis are active as aminoglycoside acetyltransferases, while only Mtb Eis functions as an N(ℇ)-acetyltransferase to acetylate Lys55 of dual-specificity protein phosphatase 16 (DUSP16)/mitogen-activated protein kinase phosphatase 7 (MKP-7), leading to the suppression of host immune responses. Here, the crystal structure of Msm Eis in the paromomycin-bound form is reported, revealing detailed interactions between an aminoglycoside antibiotic and Msm Eis. The crystal structure of Msm Eis in the paromomycin-bound form has been determined at 3.3 Å resolution. This work provides potentially useful information for structure-guided discovery of Eis inhibitors as a novel antituberculosis drug against drug-resistant Mtb.

Poly(ethylene oxide)‐graft‐methotrexate Macromolecular Drugs Conjugating via Aminopteridine Ring Exhibit Potent Anticancer Activity

AbstractWater soluble poly(ethylene oxide)‐graft‐methotrexate (PEO‐g‐MTX) conjugates with a robust amide linkage via the amine or carboxylic acid groups of MTX were designed, prepared and investigated for in vitro anti‐tumor effects. MTX was conjugated to multi‐functional PEO containing multiple pendant carboxylic acid (PEO‐g‐COOH) or amine groups (PEO‐g‐NH2) via the carbodiimide chemistry, which afforded PEO‐g‐MTX conjugates with an amide bond to the aminopteridine ring or carboxylic acid groups of MTX (denoted as PEO‐g‐MTX(COOH) and PEO‐g‐MTX(NH2), respectively). Dynamic light scattering (DLS) revealed that all PEO‐g‐MTX conjugates, with MTX contents varying from 4.8 to 19.6 wt%, existed as unimers in phosphate buffer (PB, pH 7.4, 20 mmol·L−1). Interestingly, MTT assays showed that PEO‐g‐MTX(COOH) exhibited potent anti‐tumor activity in HeLa, A549, KB and NIH3T3 cells with cytotoxicity profiles comparable to that of free MTX. In contrast, PEO‐g‐MTX(NH2) revealed diminishing cytostatic effect with IC50 (half maximal inhibitory concentration) ten to hundred times higher than that of PEO‐g‐MTX(COOH). Moreover, PEO‐g‐MTX(COOH) conjugates allowed facile conjugation with targeting ligands. Notably, folate‐decorated PEO‐g‐MTX(COOH) macromolecular drugs showed apparent targetability to folate receptor‐overexpressing KB cells with an IC50 over 12‐fold lower than non‐targeting PEO‐g‐MTX(COOH) control and about 2‐fold lower than free MTX under otherwise the same conditions.

Complex Formation and Aggregate Transitions of Sodium Dodecyl Sulfate with an Oligomeric Connecting Molecule in Aqueous Solution

Anionic single-tail surfactant sodium dodecyl sulfate (SDS) and a molecule with multiple amido and amine groups (Lys-12-Lys) were used as building blocks to fabricate oligomeric surfactants through intermolecular interactions. Their interactions and the resultant complex and aggregate structures were investigated by turbidity titration, isothermal titration microcalorimetry, dynamic light scattering, cryogenic transmission electron microscopy, freeze-fracture transmission electron microscopy, (1)H NMR, and 1D NOE techniques. At pH 11.0, the interaction between SDS and Lys-12-Lys is exothermic and mainly resulted from hydrogen bonding among the amido and amine groups of Lys-12-Lys and the sulfate group of SDS and hydrophobic interaction between the hydrocarbon chains of SDS and Lys-12-Lys. At pH 3.0, each Lys-12-Lys carries four positive charges and two hydrogen bonding sites. Then SDS and Lys-12-Lys form complexes Lys-12-Lys(SDS)6 and Lys-12-Lys(SDS)4 through the head groups by electrostatic attraction and hydrogen bonds assisted by hydrophobic interaction. Moreover, the complexes pack more tightly in their aggregates with the increase of the molar ratio. Especially the Lys-12-Lys(SDS)4 and Lys-12-Lys(SDS)6 complexes behave like oligomeric surfactants taking Lys-12-Lys as a spacer group, exhibiting a series of aggregates transitions with the increase of concentration, i.e., larger vesicles, smaller spherical micelles, and long threadlike micelles. Therefore, oligomeric surfactants Lys-12-Lys(SDS)4 and Lys-12-Lys(SDS)6 have been successfully fabricated by using a single chain surfactant and an oligomeric connecting molecule through noncovalent association.

Thermal aggregation of hen egg white lysozyme: effect of polyamines

Protein aggregation is a serious problem for both biotechnology and cell biology. Diseases such as prion misfolding, Alzheimer’s, and other amyloidosis are phenomena for which protein aggregation in our living cells is of considerable relevance. Human lysozyme has been shown to form amyloid fibrils in individuals suffering from nonneuropathic systemic amyloidosis, all of which have point mutations in the lysozyme gene. In this study, we investigated effect of small additives on the thermal aggregation of lysozyme. The main finding of this work is that multiple amine groups, spermine and spermidine, play pivotal roles in preventing the thermal aggregation of lysozyme. Our results showed that effect of spermine is more than spermidine.

Cosubstrate Tolerance of the Aminoglycoside Resistance Enzyme Eis from Mycobacterium tuberculosis

We previously demonstrated that aminoglycoside acetyltransferases (AACs) display expanded cosubstrate promiscuity. The enhanced intracellular survival (Eis) protein of Mycobacterium tuberculosis is responsible for the resistance of this pathogen to kanamycin A in a large fraction of clinical isolates. Recently, we discovered that Eis is a unique AAC capable of acetylating multiple amine groups on a large pool of aminoglycoside (AG) antibiotics, an unprecedented property among AAC enzymes. Here, we report a detailed study of the acyl-coenzyme A (CoA) cosubstrate profile of Eis. We show that, in contrast to other AACs, Eis efficiently uses only 3 out of 15 tested acyl-CoA derivatives to modify a variety of AGs. We establish that for almost all acyl-CoAs, the number of sites acylated by Eis is smaller than the number of sites acetylated. We demonstrate that the order of n-propionylation of the AG neamine by Eis is the same as the order of its acetylation. We also show that the 6' position is the first to be n-propionylated on amikacin and netilmicin. By sequential acylation reactions, we show that AGs can be acetylated after the maximum possible n-propionylation of their scaffolds by Eis. The information reported herein will advance our understanding of the multiacetylation mechanism of inactivation of AGs by Eis, which is responsible for M. tuberculosis resistance to some AGs.

Branched Multifunctional Polyether Polyketals: Variation of Ketal Group Structure Enables Unprecedented Control over Polymer Degradation in Solution and within Cells

Multifunctional biocompatible and biodegradable nanomaterials incorporating specific degradable linkages that respond to various stimuli and with defined degradation profiles are critical to the advancement of targeted nanomedicine. Herein we report, for the first time, a new class of multifunctional dendritic polyether polyketals containing different ketal linkages in their backbone that exhibit unprecedented control over degradation in solution and within the cells. High-molecular-weight and highly compact poly(ketal hydroxyethers) (PKHEs) were synthesized from newly designed α-epoxy-ω-hydroxyl-functionalized AB(2)-type ketal monomers carrying structurally different ketal groups (both cyclic and acyclic) with good control over polymer properties by anionic ring-opening multibranching polymerization. Polymer functionalization with multiple azide and amine groups was achieved without degradation of the ketal group. The polymer degradation was controlled primarily by the differences in the structure and torsional strain of the substituted ketal groups in the main chain, while for polymers with linear (acyclic) ketal groups, the hydrophobicity of the polymer may play an additional role. This was supported by the log P values of the monomers and the hydrophobicity of the polymers determined by fluorescence spectroscopy using pyrene as the probe. A range of hydrolysis half-lives of the polymers at mild acidic pH values was achieved, from a few minutes to a few hundred days, directly correlating with the differences in ketal group structures. Confocal microscopy analyses demonstrated similar degradation profiles for PKHEs within live cells, as seen in solution and the delivery of fluorescent marker to the cytosol. The cell viability measured by MTS assay and blood compatibility determined by complement activation, platelet activation, and coagulation assays demonstrate that PKHEs and their degradation products are highly biocompatible. Taken together, these data demonstrate the utility this new class of biodegradable polymer as a highly promising candidate in the development of multifunctional nanomedicine.

Ureasil–polyether hybrid film-forming materials

The objectives of this work were to study the suitability and highlight the advantages of the use of cross-linked ureasil–polyether hybrid matrices as film-forming systems. The results revealed that ureasil–polyethers are excellent film-forming systems due to specific properties, such as their biocompatibility, their cosmetic attractiveness for being able to form thin and transparent films, their short drying time to form films and their excellent bioadhesion compared to the commercial products known as strong adhesives. Rheological measurements have demonstrated the ability of these hybrid matrices to form a film in only a few seconds and Water Vapor Transmitting Rate (WVTR) showed adequate semi-occlusive properties suggesting that these films could be used as skin and wound protectors. Both the high skin bioadhesion and non-cytotoxic character seems to be improved by the presence of multiple amine groups in the hybrid molecules.

Versatile synthesis of asymmetrical dendron-like/dendron-like poly(ε-caprolactone)-b-poly(γ-benzyl-L-glutamate) block copolymers

Dendron-like/dendron-like poly(ε-caprolactone)-b-poly(γ-benzyl-L-glutamate) block copolymers with asymmetrical topology (PCL-b-PBLGn, both the subscript and the superscript denote the degree of polymerization and the branch number, respectively; n = 1, 2, and 4) were synthesized by combining ring-opening polymerization (ROP) and click chemistry. The dendron-like propargyl focal point PCL precursor with eight branches was synthesized from the controlled ROP of ε-caprolactone, and then click conjugated with azido focal point poly(amido amine) dendrons to generate the PCL-dendrons with multiple primary amine groups. The PCL-dendrons were further used as macroinitiators for the ROP of γ-benzyl-L-glutamate N-carboxyanhydride to produce the targeted asymmetrical block copolymers. Their molecular structures and physicochemical properties were thoroughly characterized by means of FT-IR, 1H NMR, gel permeation chromatography, differential scanning calorimetry, and wide angle X-ray diffraction. Both the maximal melting temperature and the degree of crystallinity of PCL block within copolymers decreased with increasing the PBLG branches and/or the chain length, demonstrating that the crystallinity of PCL block was progressively suppressed by PBLG block. Meanwhile, the PBLG block within copolymers progressively transformed from β-sheet to α-helical conformation with increasing the PBLG chain length. Consequently, this provides a versatile strategy for the synthesis of biodegradable and biomimetic block copolymers with asymmetrical dendritic topology. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Morphology-tunable architectures constructed by supramolecular assemblies of α-diimine compound: fabrication and application as multifunctional host systems

An α-diimine compound (DC) bearing multiple hydroxyl and amine groups presents excellent self-assembly behavior, yielding DC self-assemblies with tunable morphologies ranging from solid spheres, nanotubes and capsulesviahydrogen bonds and π–π stacking interactions. These DC self-assemblies provide promising multifunctional hosts for varied metal species. As a typical example, Au nanoparticles are in situ generated and accommodated into both solid and hollow DC self-assemblies by one-pot and two-step fabrication processes, respectively, resulting in the formation of solid and hollow DC/Au hybrid nanostructures. Both solid and hollow DC self-assemblies also enable host Ni(II) ions to generate DC/Ni(II) catalysts for the efficient production of porous polyethylene (PE) beads consisting of numerous PE microspheres. Moreover, the yielded PE beads replicate the textural morphologies of the original DC/Ni(II) catalysts. These DC self-assemblies also might be further utilized to host varied metal species to fabricate versatile DC/metal nanoparticle (Ag, Pt, Pd, etc.) hybrids and porous polyolefin beads with desired morphologies.

Influence of charge and structure on the coordination chemistry of copper aminoglycosides

Aminoglycosides are a family of molecules based on a 2-deoxystreptamine ring that is functionalized with a variety of sugar units that contain vicinal amine and hydroxyl functionality. These positively-charged amines promote selective high affinity binding to bacterial 16 s rRNA with resultant antibacterial activity. Aminoglycosides have also been shown to selectively target a variety of therapeutically relevant RNA motifs, and in combination with copper to promote irreversible degradation of the RNA target. The presence of multiple hydroxyl and amine groups on multiple rings creates many potential copper coordination sites. However, only a small subset of these sites actually bind copper, which have not been clearly defined experimentally, Herein we describe a more extensive structural characterization of the complexes of six aminoglycosides (kanamycin A, kanamycin B, neomycin B, neamine, tobramycin and paromomycin) that provide insights on the factors contributing to the coordination selectivity of aminoglycosides toward divalent copper. The presence of vicinal ligand donors capable of chelating the copper ion appears to be a prerequisite for stable metal binding, with charge density providing further tuning of the K(D). A possible role for metal coordination in antibacterial activity is also considered.

Thermally induced intramolecular oxygen migration of N‐oxides in atmospheric pressure chemical ionization mass spectrometry

N-Oxides are known to undergo three main thermal degradation reactions, namely deoxygenation, Cope elimination (for N-oxides containing a β-hydrogen) and Meisenheimer rearrangement, in atmospheric pressure chemical ionization mass spectrometry (APCI-MS). The ions corresponding to these thermal degradants observed in the ensuing APCI mass spectra have been used to identify N-oxides as well as to determine the N-oxidation site when the analyte contains multiple tertiary amine groups. In this paper, we report a thermally induced oxygen migration from one N-oxide amine to another tert-amine group present in the same molecule through a six-membered ring transition state during APCI-MS analysis. The observed intramolecular oxygen migration resulted in the formation of a new isomeric N-oxide, rendering the results of the APCI-MS analysis more difficult to interpret and potentially misleading. In addition, we observed novel degradation behavior that happened after the Meisenheimer rearrangement of the newly formed N-oxide: a homolytic cleavage of the N-O bond instead of elimination of an aldehyde or a ketone that usually follows the rearrangement. Understanding of these unusual degradation pathways, which have not been reported previously, should facilitate structural elucidation of N-oxides using APCI-MS analysis.

A fluorescent guest encapsulated by a photoreactive azobenzene dendrimer

We have studied the adduct formed by N,N′-2,7-didecyldiazapyrenium (P2+), as the hexafluorophosphate salt, with a third generation dendrimer (D) that comprises 14 tertiary amine units in the interior, and 16 naphthyl and 16 trans-azobenzene units in the periphery. A strong charge-transfer interaction between the electron-accepting diazapyrenium dication and electron-donating amine units of the dendrimer interior leads to a host–guest complex with 1 : 1 stoichiometry, namely D(16t)⊃P2+. The self-assembly process can be easily monitored by strong changes in the absorption and emission spectra: (i) new absorption bands (λmax ≈ 445 and 565 nm) at lower energy compared to the isolated species arise, (ii) a strong quenching of the intense diazapyrenium fluorescence is observed, and (iii) a new broad emission band, typical of the charge-transfer complex, appears with a maximum at 660 nm at 298 K and 600 nm at 77 K. By global analysis of the absorption spectra, an association constant of 1.0 × 106 M−1 is obtained for D(16t)⊃P2+, compared to 3.0 × 104 M−1 in the case of the adduct of P2+ with triethylamine under the same experimental conditions. This result demonstrates that the presence of bulky substituents at the dendrimer periphery does not hinder the formation of a stable complex and suggests a cooperative effect due to the multiple amine groups of the dendrimer branching points. No energy transfer from the azobenzene or naphthyl chromophores to the charge-transfer complex has been evidenced. The self-assembly process can be reversed upon addition of an equimolar amount of trifluoromethanesulfonic acid. An adduct with 1 : 1 stoichiometry is formed also between P2+ and D(2t14c), a species obtained from D(16t) upon irradiation at 365 nm: the corresponding association constant is very similar to that of D(16t)⊃P2+, showing that the isomeric state of the peripheral azobenzene units does not affect the stability of the adduct.

Synthesis, characterization and DNA binding studies of a polymer-cobalt(III) complex containing the 2,2′-bipyridyl ligand

The polymer-cobalt(III) complex, cis-[Co(bpy) 2(BPEI)Cl]Cl 2 · 4H 2O (bpy = 2,2′-bipyridine, BPEI = branched polyethyleneimine) has been synthesised and characterized. Binding of this polymer-cobalt(III) complex with calf thymus DNA(CT-DNA) was investigated by UV–Visible absorption and fluorescence spectroscopic techniques. Also the interaction of pBR322 DNA with the same polymer-cobalt(III) complex was studied using the gel electrophoresis method. The results indicate that the polymer-cobalt(III) complex interacts with DNA very strongly ( K b = 5.12 × 10 5 M −1 and K sv = 0.2023). The nature of the binding seems to be mainly an electrostatic interaction between DNA and the polymer-cobalt(III) complex. Other binding modes, such as hydrogen bonds, may also exist in this system. The high binding constant values indicate the operation of cooperative effects between multiple cobalt(III) complex molecular units and free amine groups, which are present in a single polymer molecule, in binding to DNA.

Experimental Design Optimization of Filamentous Phage Transfection into Mammalian Cells by Cationic Lipids

A previous study showed that filamentous phage could be efficiently transfected into mammalian cells in the presence of the cationic lipid Transfectam. In the present study, we used an experimental plan based on a uniform network (Doehlert) matrix to estimate optimal transfection conditions in two different cell lines, CHO and Cos-7. Using the cationic lipid RPR120535b as a model, we show that optimal conditions can be determined much more readily than with standard response curves. Under optimal conditions as analyzed by FACS, up to 60% of Cos-7 and 50% of CHO cells can be transfected. Furthermore, a comparison of different lipids (Transfectam, RPR120535b, TC1-12 and GAP-DLRIE/DOPE) suggests that lipids with multiple amine groups are more efficient for the transfection of filamentous phage.

Bridged cobalt amine complexes induce DNA conformational changes effectively

Cobalt(III) hexaamine ion [Co(NH 3) 6] 3+ is known to facilitate the transition of B- to Z-DNA or B- to A-DNA depending on the DNA sequences. Specific interactions are found between the amines of [Co(NH 3) 6] 3+ and DNA atoms of A-DNA or Z-DNA. Bridged Co(III)pentaamine complexes, with multiple amine groups arranged in a rigid framework, may enhance the effectiveness of the conformational transition by occupying simultaneously two of the Co(III)hexaamine binding sites. Therefore, the imidazole-bridged Co(III)pentaamine complexes have been synthesized and their interactions with DNA oligonucleotides investigated by circular dichroism (CD) and NMR spectroscopy. CD studies of the titrations of d(A 2C 15G 15T 2) with [(NH 3) 5Co(Im) Co(NH 3) 5]Br 5 and [{(NH 3) 5Co(Im)} 2Co(NH 3) 4]Br 7 showed that the former metal compound indeed is more effective than [Co(NH 3) 6] 3+ in inducing the transition from B- to A-DNA. The conversion of B- to A-DNA was also supported by one- and two-dimensional NMR studies. Similarly for the titrations of poly(dC-dG)·poly(dC-dG) and d(m 5 C-G) 15 with these two bridged Co(III) complexes, efficient induction of Z-DNA was observed. Our studies suggest that bridged Co(III)pentaamine complexes may be useful agents for studying nucleic acid structures.

Solid phase synthesis of 5′ non radioactive multiple labelled oligodesoxyribonucleotides.

The convenient solid phase synthesis of oligodesoxyribonucleotides carrying multiple amine groups at their 5′ end was described using a branching lysine core. The possibility of attachment of non radioactive label was demonstrated by synthesis of a 5′-tetrathymidilate. The identity of the derivatives was proved by Plasma Desorption Mass Spectrometry. The convenient solid phase synthesis of oligodeoxyribonucleosides carrying multiple amine groups at their 5′ end was described using a branching lysine core. The possibility of attachment of non radioactive label was demonstrated by synthesis of a 5′-tetrathymidilate. The identity of the derivatives was proved by Plasma Desorption Mass Spectrometry