Gene/Protein Disease Symptom Drug Enzyme Compound
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In this study, we demonstrate that 2-microm-sized Ag (microAg) powders can be used as a core material for constructing molecular sensing/recognition units operating via surface-enhanced Raman scattering (SERS). This is possible because microAg powders are very efficient substrates for both the infrared and Raman-spectroscopic characterization of molecular adsorbates prepared in a similar manner on silver surfaces; we can obtain an infrared spectrum of organic molecules adsorbed on microAg particles with a very high signal-to-noise ratio by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and the Raman spectrum of organic monolayers on powdered silver is an SERS spectrum. The agglomeration of microAg particles in a highly concentrated buffer solution could be prevented by the layer-by-layer deposition of cationic and anionic polyelectrolytes such as poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA). In fact, prior to depositing PAA and PAH, 4-aminobenzenethiol (4-ABT) was assembled on the surfaces of the microAg particles as SERS markers. Because of the presence of amine groups of 4-ABT, PAA could be readily deposited on the microAg particles. On the other hand, the outermost PAA layer could also be derivatized with biotin-derivatized poly(L-lysine). The nonspecific interaction of poly(L-lysine) with proteins could be suppressed by grafting poly(ethylene glycol) into the biotin-derivatized poly(L-lysine) molecules. On the basis of the nature of the SERS peaks of 4-ABT, it was confirmed that these biotinylated microAg powders were effective in selectively recognizing the streptavidin arrays. Because a number of different molecules can be used as SERS-marker molecules, such as probable 4-ABT, commercially available microAg powders must be a prospective material in molecular sensing/recognition, particularly via SERS.
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PMID:Silver-particle-based surface-enhanced Raman scattering spectroscopy for biomolecular sensing and recognition. 1654 10

Layer-by-layer (LBL) polyelectrolyte films were constructed from poly(L-glutamic acid) (PGA) and poly(L-aspartic acid) (PAA) as polyanions, and from poly(L-lysine) (PLL) as the polycation. The terminating layer of the films was always PLL. According to attenuated total reflection Fourier transform infrared measurements, the PGA/PLL and PAA/PLL films, despite their chemical similarity, had largely different secondary structures. Extended beta-sheets dominated the PGA/PLL films, while alpha-helices and intramolecular beta-sheets dominated the PAA/PLL films. The secondary structure of the polyelectrolyte film affected the adsorption of human serum albumin (HSA) as well. HSA preserved its native secondary structure on the PGA/PLL film, but it became largely deformed on PAA/PLL films. Both PGA and PAA were able to extrude to a certain extent the other polyanion from the films, but the structural consequences were different. Adding PAA to a (PGA/PLL)5-PGA film resulted in a simple exchange and incorporation: PGA/PLL and PAA/PLL complexes coexisted with their unaltered secondary structures in the mixed film. The incorporation of PGA into a (PAA/PLL)5-PAA film was up to 50% and caused additional beta-structure increase in the secondary structure of the film. The proportions of the two polyanions were roughly the same on the surfaces and in the interiors of the films, indicating practically free diffusion for both polyanions. The abundance of PAA/PLL and PGA/PLL domains on the film surfaces was monitored by the analysis of the amide I region of the infrared spectrum of a reporter molecule, HSA, adsorbed onto the three-component polyelectrolyte films.
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PMID:Partial poly(glutamic acid) <--> poly(aspartic acid) exchange in layer-by-layer polyelectrolyte films. Structural alterations in the three-component architectures. 1676 5

Novel thermosensitive polyion complex (PIC) micelles were prepared in an aqueous medium based on the complexation of a pair of oppositely charged block ionomers, poly(2-isopropyl-2-oxazoline)-b-poly(amino acid)s (PiPrOx-b-PAA), containing thermosensitive PiPrOx segments. The controlled synthesis of PiPrOx-b-PAA was achieved via the ring-opening anionic polymerization of N-carboxyanhydrides (NCA) of either eta-benzyloxycarbonyl-l-lysine (Lys(Z)-NCA) or beta-benzyl-l-aspartate (BLA-NCA) with omega-amino-functionalized PiPrOx macroinitiators and the subsequent deprotection reaction under acidic or basic conditions. Gel permeation chromatography (GPC) and 1H NMR spectroscopy revealed that the syntheses of two block ionomers, poly(2-isopropyl-2-oxazoline)-b-poly(l-lysine) [PiPrOx-P(Lys)] and poly(2-isopropyl-2-oxazoline)-b-poly(aspartic acid) [PiPrOx-P(Asp)], proceeded almost quantitatively to give samples with a narrow molecular weight distribution (Mw/Mn </= 1.2). The mixing of these two oppositely charged block ionomers in an aqueous medium led to the spontaneous formation of PIC micelles, which was confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The PIC micelles were spherical particles with a narrow distribution in the range of the measured concentration (0.125-1 mg/mL) and were stable without any secondary aggregates. Furthermore, the PIC micelles had a constant cloud-point temperature (Tcp) of approximately 32 degrees C under physiological conditions regardless of the total concentration, suggesting that the concentration factor is almost negligible with respect to the Tcp of the micelles presumably because of the increased local concentration of the PiPrOx segments in the shell layer. These PIC micelles have a promising application as a size-regulated smart nanocontainer loading charged compounds as well as bearing a thermosensitive outer shell that is useful for physical affinity control.
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PMID:Preparation and characterization of polyion complex micelles with a novel thermosensitive poly(2-isopropyl-2-oxazoline) shell via the complexation of oppositely charged block ionomers. 1719 Apr 96

Bovine Type I collagen was investigated, building on a large scale computer model of a collagen fibril in water, and focusing on two stages of the leather manufacturing process. The effects of different salts (NaCl, CaCl(2), and Na(2)SO(4)) on the swelling behavior of collagen at low pH (the pickling process) were studied. The salts suppress the swelling of the fibrils at low pH and we find specific stabilizing influences for CaCl(2) and Na(2)SO(4), due to weak Ca(2+)/Cl(-) and strong SO(4) (2-)/lysine/arginine interactions, respectively. Using state-of-the-art sampling techniques, such as the metadynamics algorithm, to allow an efficient exploration of configuration space, we were able to investigate the effect of polyacrylate and poly(methyl acrylate) - two polymeric retanning agents - on the fibril. Both polymers interact with the ammonium groups on the surface, but polyacrylate shows significantly stronger interactions. We suggest that it is this stronger interaction that contributes to the reduced suitability of PAA as a tanning agent.
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PMID:Modeling of bovine type-I collagen fibrils: interaction with pickling and retanning agents. 1729 96

We demonstrate in this work that 2-microm-sized Ag (microAg) powders can be used as a core material for constructing biomolecular sensing/recognition units operating via surface-enhanced resonance Raman scattering (SERRS). This is possible because microAg powders are very efficient substrates for both the diffuse reflectance IR and the surface-enhanced Raman scattering-SERRS spectroscopic characterization of molecular adsorbates prepared in a similar manner on silver surfaces. Besides, the agglomeration of microAg particles in a buffer solution can be prevented by the layer-by-layer deposition of cationic and anionic polyelectrolytes such as poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA). In this particular study, we used rhodamine B isothiocyanate (RhBITC) as a SERRS marker molecule, and microAg powders adsorbed consecutively with RhBITC and PAH-PAA bilayers were finally derivatized with biotinylated poly(L-lysine). On the basis of the nature of the SERRS peaks of RhBITC, those microAg powders were confirmed to selectively recognize streptavidin molecules down to concentrations of 10(-10) g mL-1. Since a number of different molecules can be used as SERS-SERRS marker molecules, the present method proves to be an invaluable tool for multiplex biomolecular sensing/recognition via SERS and SERRS.
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PMID:Silver-particle-based surface-enhanced resonance Raman scattering spectroscopy for biomolecular sensing and recognition. 1731 10

This paper describes the preparation, characterization, and enzymatic activity of complex coacervate core micelles (C3Ms) composed of poly(acrylic acid) (PAA) and poly(N-methyl-2-vinyl pyridinium iodide)-b-poly(ethylene oxide) (PQ2VP-PEO) to which the antibacterial enzyme lysozyme is end-attached. C3Ms were prepared by polyelectrolyte complex formation between PAA and mixtures containing different ratios of aldehyde and hydroxyl end-functionalized PQ2VP-PEO. This resulted in the formation of C3Ms containing 0-40% (w/w) of the aldehyde end-functionalized PQ2VP-PEO block copolymer (PQ2VP-PEO-CHO). Chemical conjugation of lysozyme was achieved via reductive amination of the aldehyde groups, which are exposed at the surface of the C3M, with the amine groups present in the side chains of the lysine residues of the protein. Dynamic and static light scattering indicated that the conjugation of lysozyme to C3Ms prepared using 10 and 20% (w/w) PQ2VP-PEO-CHO resulted in the formation of unimicellar particles. Multimicellar aggregates, in contrast, were obtained when lysozyme was conjugated to C3Ms prepared using 30 or 40% (w/w) PQ2VP-PEO-CHO. The enzymatic activity of the unimicellar lysozyme-C3M conjugates toward the hydrolysis of the bacterial substrate Micrococcus lysodeikticus was comparable to that of free lysozyme. For the multimicellar particles, in contrast, significantly reduced enzymatic rates of hydrolysis, altered circular dichroism, and red-shifted tryptophan fluorescence spectra were measured. These results are attributed to the occlusion of lysozyme in the interior of the multimicellar conjugates.
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PMID:Complex coacervate core micelles with a lysozyme-modified corona. 1758 20

End-tethered cationic polypeptide brushes of poly(L-lysine) (t-PLL) were combined with three anionic polymers, poly(acrylic acid) (PAA), poly(L-glutamic acid) (PLGA), and poly(L-aspartic acid) (PLAA), to form reversible polyelectrolyte complex films at surfaces at neutral pH. The polyelectrolyte complex formation was confirmed by an in situ zeta-potential study and by positive fluorescent images after adding prelabeled anionic polymers. The secondary conformations of the t-PLL complex films depend upon the specific polyelectrolyte with which t-PLL was coupled as studied by circular dichroism and FTIR. Specifically, the random coil chain configuration of the t-PLL film was converted to an alpha-helical, beta-sheet, or random coil structure after forming complexes with PAA, PLGA, or PLAA, respectively. Each of these complexes could be returned to the original random coil t-PLL structure by a dilute acid rinse. Additional thickness and morphological studies from ellipsometry and atomic force microscopy have further shown that the corresponding film thicknesses of the individual solvated films were affected more by the secondary structures in films than by the adsorbed mass or surface net charges. The solvated thickness was reduced significantly after the random coil t-PLL film was coupled with polyanions in forming compact regulated structures in films. This biomimetic approach provides a new opportunity for controlling the molecular organization in surface macromolecular assemblies and may provide a model for structural study of protein complexes on a chip.
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PMID:Controlled molecular organization of surface macromolecular assemblies based on stimuli-responsive polypeptide brushes. 1905 8

Highly efficient antibody immobilization is crucial for conducting high-performance immunoassays such as enzyme-linked immunosorbent assay (ELISA) in microarray and microfluidic biochips. In this study, a biotin-poly(L-lysine)-g-poly(ethylene glycol) (biotin-PLL-g-PEG) and protein A-based technique was developed to immobilize antibody on the surface of poly(methyl methacrylate) (PMMA) microchannels. First, PMMA surface was activated by oxygen plasma, followed by poly(acrylic acid) (PAA) grafting to add functional carboxyl group for subsequent binding. After the biotin-PLL-g-PEG molecules reacted with carboxyl groups through the electrostatic interactions, biotinylated protein A was immobilized on the surface through a linking molecule, neutravidin. To evaluate the applicability of this novel immobilization strategy, human interferon-gamma (IFN-gamma) was used as a model protein. Since protein A could better control the immobilization orientation, and the combination of biotin-PLL-g-PEG and PLL-g-PEG could adjust the conformation of antibodies, antigen capture efficiency and detection signals were significantly improved on the microchips by using this strategy. The optimal grafting conditions were also experimentally determined: the biotin grafting ratio of 0.189 in the PLL-g-PEG molecule and the mixture ratio of 85% (biotin-PLL-g-PEG to PLL-g-PEG). This surface modification can be applied for targeted drug delivery, biosensor and other immunoassay applications.
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PMID:Specific antibody immobilization with biotin-poly(L-lysine)-g-poly(ethylene glycol) and protein A on microfluidic chips. 1964 44

Improved glucagon-like peptide-1 (GLP-1) receptor activation is considered one of the most effective targets for antidiabetic therapy. For this purpose, we modified the GLP-1 analog of exendin-4 using two fatty acids (FA) either lauric acid (LUA, C12) or palmitic acid (PAA, C16) at its two lysine residues, to produce; Lys(12)-FA-Exendin-4 (FA-M2), Lys(27)-FA-Exendin-4 (FA-M1), or Lys(12,27)-diBA-Exendin-4 (FA-Di). The structural, biological, and pharmaceutical characteristics of these exendin-4 analogs were then investigated. Biological activity tests demonstrated that LUA-M1 had well-preserved in vivo antidiabetic activity and in vitro insulinotropic activity with minimum GLP-1 receptor binding affinity loss as compared with exendin-4. Furthermore, pharmacokinetic studies in rats revealed that s.c. administration of LUA-M1 significantly enhanced pharmacokinetic parameters, such as, elimination half-life, mean residence time, and AUC values as compared with exendin-4. The protracted antidiabetic effects of LUA-M1 were also confirmed by prolonged normoglycemia observed in type 2 diabetic mice (20nmol/mouse single injection of exendin-4 or LUA-M1 induced normoglycemia for 6 or 24h, respectively). These findings suggest that FA conjugated exendin-4s should be considered potential candidates for the treatment of diabetes.
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PMID:The fatty acid conjugated exendin-4 analogs for type 2 antidiabetic therapeutics. 2009 59

Collagen, which is used as a biomaterial, is the most abundant protein in mammals. We have previously reported that a dendrimer modified with collagen model peptides, (Gly-Pro-Pro)(5), formed a collagen-like triple-helical structure, showing thermal reversibility. In this study, various collagen-mimic dendrimers of different generations and at different binding ratios were synthesized, to investigate the relationship between the peptide clustering effect and the higher order structure formation. The formation of the higher order structure was influenced by the binding ratios of the peptide to the dendrimer, but was not influenced by the dendrimer generation. A spacer, placed between the dendrimer terminal group and the peptide, negatively contributed to the formation of the higher order structure. The collagen model peptides were also attached to poly(allylamine) (PAA) and poly-L-lysine (poly(Lys)) to compare them with the collagen-mimic dendrimers. The PAA-based collagen-mimic compound, bearing more collagen model peptides than the dendrimer, exhibited a thermally stable higher order structure. In contrast, this was not observed for the collagen-mimic polymers based on poly(Lys). Therefore, dendrimers and vinyl polymers act as a scaffold for collagen model peptides and subsequently induce higher order structures.
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PMID:Higher order structure of short collagen model peptides attached to dendrimers and linear polymers. 2016 22


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