SEARCH · PubMed Health

Results for “Spectroscopy, Fourier Transform Infrared”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,333 records · Page 74Linked to original sources

PubMed1999

Changes in secondary structure and salt links of cytochrome P-450cam induced by photoreduction: a Fourier transform infrared spectroscopic study.

Tris(2,2'-bipyridyl)ruthenium(II) was used as a light-induced artificial electron donor for the transfer of the first electron to cytochrome P-450(cam) bound with (1R)-camphor and camphane substrates, and in the substrate-free form. Fourier transform infrared spectroscopy was used to detect changes of the amide I' band and the CO ligand stretch vibration of heme-bound carbon monoxide associated with the heme redox transition. The reduced-minus-oxidized difference spectra show that not only the heme group but also the protein backbone and individual amino acid side chains were affected by the redox transition. Observed secondary structure changes were almost identical for (1R)-camphor-bound and camphane-bound cytochrome P-450(cam), with a remarkable negative signal at 1724.3 cm(-)(1) and a positive signal at 1716.0 cm(-)(1). These signals were not observed in substrate-free P-450(cam). On the basis of known crystallographic data, we assign these signals to a change of hydrogen bonds of a salt link between Arg112, His355, and the heme 6-propionic group.

2,2'-Dipyridyl↗

PubMed1997

Evidence for proton transfer from Glu-46 to the chromophore during the photocycle of photoactive yellow protein.

Photoactive yellow protein (PYP) belongs to the novel group of eubacterial photoreceptor proteins. To fully understand its light signal transduction mechanisms, elucidation of the intramolecular pathway of the internal proton is indispensable because it closely correlates with the changes in the hydrogen-bonding network, which is likely to induce the conformational changes. For this purpose, the vibrational modes of PYP and its photoproduct were studied by Fourier transform infrared spectroscopy at -40 degrees C. The vibrational modes characteristic for the anionic p-coumaryl chromophore (Kim, M., Mathies, R. A., Hoff, W. D., and Hellingwerf, K. J. (1995) Biochemistry 34, 12669-12672) were observed at 1482, 1437, and 1163 cm-1 for PYP. However, the bands corresponding to these modes were not observed for PYPM, the blue-shifted intermediate, but the 1175 cm-1 band characteristic of the neutral p-coumaryl chromophore was observed, indicating that the phenolic oxygen of the chromophore is protonated in PYPM. A 1736 cm-1 band was observed for PYP, but the corresponding band for PYPM was not. Because it disappeared in the Glu-46 --> Gln mutant of PYP, this band was assigned to the C=O stretching mode of the COOH group of Glu-46. These results strongly suggest that the proton at Glu-46 is transferred to the chromophore during the photoconversion from PYP to PYPM.

Bacterial Proteins↗

PubMed2004

Structural dynamics controls nitric oxide affinity in nitrophorin 4.

Nitrophorin 4 (NP4) is one of seven nitric oxide (NO) transporting proteins in the blood-sucking insect Rhodnius prolixus. In its physiological function, NO binds to a ferric iron centered in a highly ruffled heme plane. Carbon monoxide (CO) also binds after reduction of the heme iron. Here we have used Fourier transform infrared spectroscopy at cryogenic temperatures to study CO and NO binding and migration in NP4, complemented by x-ray cryo-crystallography on xenon-containing NP4 crystals to identify cavities that may serve as ligand docking sites. Multiple infrared stretching bands of the heme-bound ligands indicate different active site conformations with varying degrees of hydrophobicity. Narrow infrared stretching bands are observed for photodissociated CO and NO; temperature-derivative spectroscopy shows that these bands are associated with ligand docking sites close to the extremely reactive heme iron. No rebinding from distinct secondary sites was detected, although two xenon binding cavities were observed in the x-ray structure. Photolysis studies at approximately 200 K show efficient NO photoproduct formation in the more hydrophilic, open NP4 conformation. This result suggests that ligand escape is facilitated in this conformation, and blockage of the active site by water hinders immediate reassociation of NO to the ferric iron. In the closed, low-pH conformation, ligand escape from the active site of NP4 is prevented by an extremely reactive heme iron and the absence of secondary ligand docking sites.

Animals↗

PubMed2005

Influence of deposition parameters on chemical properties of calcium phosphate coatings prepared by using electrostatic spray deposition.

The electrostatic spray deposition (ESD) technique offers the possibility of depositing calcium phosphate (CaP) coatings onto various substrate materials with defined chemical and morphological properties. The relationship between physical, apparatus-related deposition parameters, and the chemical characteristics of ESD coatings was investigated by means of X-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy to be able to deposit CaP coatings with tailored chemical properties. The results showed that the chemical characteristics of CaP coatings, deposited with use of the ESD technique, were strongly dependent on the deposition temperature, the nozzle-to-substrate distance, the liquid flow rate, and the geometry of the spraying nozzle. By investigating the influence of the deposition temperature, information could be obtained on the formation mechanism of CaP coatings-and specifically the biologically interesting carbonate apatite phase-using the ESD technique. CaP coatings were not formed merely because of solvent evaporation; a chemical reaction was needed to synthesize the coatings. This reaction involved thermal decomposition of the organic solvent butyl carbitol into carbonate ions via formation of intermediate oxalate ions. The amount of carbonate incorporation, and consequently, the Ca/P ratios of the deposited coatings, was shown 1) to decrease with increasing nozzle-to-substrate distance, 2) to decrease with increasing liquid flow rate, and 3) to decrease by making use of a novel two-component nozzle geometry.

Calcium Phosphates↗

PubMed2003

Antibacterial activity and bonding characteristics of an adhesive resin containing antibacterial monomer MDPB.

OBJECTIVES: The aims of this study were to investigate the antibacterial activity of an adhesive resin incorporating the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) as well as its bonding characteristics in terms of bond strength into dentin and curing ability. METHODS: An experimental adhesive resin was prepared by incorporation of 2.5% MDPB into proprietary adhesive (LB Bond), and the inhibitory effect of cured specimen against the growth of Streptococcus mutans on its surface was determined. Bond strength to human dentin and degree of conversion of the experimental adhesive in combination with 1, 2, or 5% MDPB-containing primers, which were previously reported to possess bactericidal effect, were evaluated by conventional tensile bond strength test and Fourier transformation infrared spectroscopy. RESULTS: The cured experimental adhesive exhibited an inhibitory effect on S. mutans growth, reducing the number of bacteria to approximately 3% of control adhesive without MDPB. Tensile bond strength of experimental adhesive was not significantly different from that of the control (p>0.05), and use in combination with MDPB-containing primer did not show any adverse influence on bond strength. The degree of conversion of the bonding system was not different (p>0.05) between control and experimental adhesive irrespective of addition of MDPB into primer. SIGNIFICANCE: These results indicate that an adhesive resin with antibacterial activity after curing could be produced by incorporation of MDPB without influencing bond strength or curing performance, suggesting that the comprehensive bonding system including MDPB-containing primer and adhesive should be highly effective in its antibacterial effect before and after curing.

Acid Etching, Dental↗

PubMed2006

Evaluation of poly{-N-isopropylacrylamide-co-[3-(methacryloylamino)propyl]trimethylammonium} as a stationary phase for capillary electrochromatography.

A cationic polyacrylamide-based stationary phase was synthesized and characterized for CEC. The stationary phase was prepared by radical copolymerization of N-isopropylacrylamide (NIPAAm) and (3-(methacryloylamino)propyl)trimethylammonium chloride (MAPTA), producing a copolymer attached to 5 microm porous silica particles. Fourier transform infrared spectroscopy and thermogravimetric analysis were used to characterize the copolymer. Under capillary electrochromatographic conditions, the poly-NIPAAm-co-MAPTA stationary phase showed to be stable in a wide pH range. The amino groups in the MAPTA provided an anodic EOF for CEC separation. The electroosmotic mobility changed less than 10% when the pH of the mobile phase was changed from 2 to 12. The run-to-run RSD of analyte migration time was less than 1.5% (n = 3), and the RSD of peak area was less than 3% (n = 3). The day-to-day RSD for migration time was less than 2% (n = 3). The polar groups present in the stationary phase contributed to the selectivity of the phase providing for hydrophilic interactions. In the separation of a series of neutral and acidic compounds, the stationary phase shows a mixed-mode separation mechanism with both hydrophobicity and hydrophilicity contributing to the separation.

Acrylamides↗

PubMed2007

Mechanical and biocompatible influences of chitosan fiber and gelatin on calcium phosphate cement.

Calcium phosphate cement (CPC) is a widely used bone substitute in the clinic; however, the low strength of CPC limits its utilization. In this study, we investigated mechanical influences of chitosan fiber combined with gelatin on CPC, and examined the biocompatibility of the new composite with rat bone marrow stromal cells. Compared to the fiber impregnated in phosphate buffered saline (80.5 MPa), our study showed that tensile strength of chitosan fiber increased 106 and 114% with the impregnation of gelatin at the mass fraction 5 and 10%, although this increase was not statistically significant. It was demonstrated by Fourier transform infrared spectroscopy that the characteristic absorption bands of chitosan were changed with the addition of gelatin. The optimal flexural strength enhancement was obtained when CPC was reinforced with fiber at volume fraction of 30% and gelatin at mass fraction of 5% (maximum: 12.31 MPa). The fiber morphology was more compact when the chitosan fibers impregnated with gelatin at mass fraction of 5 or 10% than chitosan alone. The fracture analysis showed that the new CPC-chitosan fiber-gelatin composite presented many remnants of CPC adhered to fibers. Short minimum essential medium extract test showed no cell growth inhibition after the addition of the new composite. Rat bone marrow stromal cells retain the ability to spread and grow on the composite. Our studies demonstrated that the flexural strength is greatly increased by using CPC incorporated with proper ratio of CF and gelatin. More over, the new composite demonstrated biocompatibility in vitro.

Animals↗

PubMed2006

Physicochemical characterization of papain entrapped in ionotropically cross-linked kappa-carrageenan gel beads for stability improvement using Doehlert shell design.

This work examines the influence of various process parameters on papain entrapped in cross-linked kappa-carrageenan beads for improvement of its stability. A Doehlert shell design (DSD) was employed to investigate the effect of three process variables, namely kappa-carrageenan concentration, KCl concentration, and hardening time, on the entrapment, time required for 50% enzyme release (T50), time required for 90% enzyme release (T90), and particle size. The beads were prepared by dropping the kappa-carrageenan containing papain into a magnetically stirred KCl solution. Topographical characterization was carried out by scanning electron microscopy and entrapment was confirmed by Fourier transform infrared spectroscopy and differential scanning calorimetry. Stability testing was carried out according to the International Conference on Harmonization (ICH) guidelines for zone III and IV. A polymeric matrix was prepared with kappa-carrageenan (3.5% w/v) and potassium chloride (0.5 M) using the ionotropic gelation method, with a hardening time of 20 min. Beads characterized by a spherical disc shape with a collapsed center, an absence of aggregates, an entrapment of 82.75%, a T90 value of 55.36 min, and a composite index of 88.55 were produced. The shelf-life of the enzyme-loaded beads was found to increase to 3.63 years compared with 1.01 years for the conventional formulation. It can be inferred that the proposed methodology can be used to prepare papain-loaded kappa-carrageenan beads for stability improvement.

Algorithms↗

PubMed1995

Oxidative biodegradation mechanisms of biaxially strained poly(etherurethane urea) elastomers.

As part of ongoing studies in polyurethane biostability and biodegradation, we have investigated an in vitro system to test strained poly(etherurethane urea) (PEUU). Recently, we utilized this system to reproduce in vivo stress cracking in strained Pellethane. In this study, strained PEUU was tested to determine whether it degrades through a common mechanism with Pellethane and to further examine the steps involved in this degradation. Biaxially strained PEUU elastomers were treated with an alpha 2-macroglobulin (alpha 2-Mac) protein solution followed by an oxidative H2O2/CoCl2 treatment. Characterization of the strained PEUU specimens was performed with attenuated total reflectance-Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), electron spectroscopy for chemical analysis, and contact angle analysis. The results from these characterization techniques provide conclusive evidence that biodegradation of PEUU and Pellethane occurs through a common mechanism. Chemical changes to the PEUU include cleavage of the polyether soft segments and urethane linkages, leaving the hard segment domains unaffected. SEM analysis shows that this chain cleavage leads to the development of severe pitting and cracking of the PEUU surface. In addition, the in vitro degradation accurately reproduces the in vivo degradation chemically and physically. This result verifies that the primary species responsible for biodegradation of PEUUs, in vivo, are hydroxyl and/or hydroperoxide radicals. alpha 2-Mac pretreatment increases the rate of degradation compared to direct treatment in H2O2/CoCl2. As the PEUU soft segment chains are cleaved, the degradation products are extracted into the treatment solution or environment. Finally, a new biodegradation mechanism of PEUUs is presented that involves crosslinking of the polyether soft segments.

Adsorption↗

PubMed1995

Mapping the intersubunit region of influenza virus hemagglutinin: comparative CD and FTIR spectroscopic studies on multiple antigenic peptides.

An A/PR/8/34 (IHN1) influenza virus hemagglutinin (HA)-specific monoclonal antibody (Z38) was found to react with the solid phase adsorbed influenza virus expressing uncleaved (HA0) molecules but not to bind to virus particles bearing enzymatically cleaved hemagglutinin. Synthetic peptides corresponding to the uncleaved HA0 317-341 intersubunit region of subtypes H1-H3 (IP1-IP3) or comprising either the C-terminal 317-329 amino acids of HA1 (CP1) or the N-terminal 330-341 of HA2 (fusion peptide, FP) subunits of cleaved HA were used to characterize the fine specificity of Z38 mAb. Circular dichroism and Fourier-transform infrared spectroscopy showed that, compared to IP2 and IP3 comprising the H2 and H3 subtype fragments of the intact intersubunit region, IP1 has relatively low helicity but a tendency to adopt beta-turns in trifluoroethanol. The immunological and conformational properties of multiple antigenic peptides (MAPs) containing four copies of CP1 were also studied. Based on the appearance of an infrared component band at 1637 cm-1 (beta-turn band), the CP1 arms of MAPs also contain repeats of beta-turns. However, it is only the MAP1-FP construct comprising also the fusion peptide, which binds Z38 mAb as strongly as IP1 does. This puts emphasis on the role of the fusion region in modifying conformation and consequently the ability of peptides to elicit an antibody response. The results obtained for peptide conformation also suggests a beta-turn(s)/beta-sheet/beta-turn/beta-sheet conformational motif in the recognition by the hemagglutinin subtype-specific Z38 monoclonal antibody or by peptide-induced polyclonal antibodies.

Amino Acid Sequence↗

PubMed1998

Fourier transform infrared (FT-IR) spectroscopic studies of peptide models for interaction of the binding regions of high molecular weight kininogen and prekallikrein.

The binding sites for high molecular weight kininogen (HK) on prekallikrein (PK) are composed of two discontinuous segments in the primary sequence, one in Apple 1 domain (PK56=F56-G86) and the other in Apple 4 (PK266=K266-G295). The site on HK, HK31, is subsumed in a 31-amino-acid sequence (S565-K595) near the C-terminus which has the same affinity for prekallikrein as the entire HK molecule. The binding among them is likely due to conformational changes which serve to juxtapose the PK binding domain within HK with the HK binding site. Resolution-enhanced Fourier transform infrared spectroscopy (FT-IR) has been employed to analyze the contents of secondary structural elements of PK56 and HK31 and to reveal the possible specific binding portion and structural changes in HK31 and PK56 upon binding. From the amide I bands of their deconvoluted FT-IR spectra, it is known that PK56 contains no helix component, while HK31 has two different helical conformations. A quantitative comparison of the spectra of HK31, PK56 and their binding complex suggests that the conformation of 3(10)-helix in HK31 has been changed to an alpha-helix, and one disordered segment of PK56 may have been changed to extended conformation. The other structural components in PK56 and HK31 remain unchanged. Since previous studies have shown that these peptides mimic the natural protein in their bioactivity, their interaction may reflect similar changes in the natural molecules.

Amino Acid Sequence↗

PubMed2004

Preliminary study of lake dissolved organic matter in light of nanoscale supramolecular assembly.

Large-scale preparative high-performance size-exclusion chromatography (HPSEC) was performed to separate different molecular size fractions in milligram quantities from strongly colored dissolved organic matter (DOM) of a freshwater using a very mild conjugate acid-base pair (10 mM acetic acid-sodium acetate solution at pH 7.0 with an ionic strength of 6 x 10(-5)) as the mobile phase. The homogeneity-uniformity of different molecular size fractions in relation to their combined original mixture was verified by an analytical HPSEC system. In addition to molecular size distribution and basic spectroscopic characteristics, Fourier transform infrared spectroscopy was applied to specify structural features for different size fractions. The results demonstrate clearly that only a very small amount of conjugate organic acid-base pair is required to generate a powerful resolution for a DOM mixture, and very strong treatments with organic acids are not necessarily needed to reach a better SEC resolution. Most essential is the combined outcome of different HPSEC experiments and determined structural functionalities which indicate that almost all original DOM solutes are aggregated mixtures consisting of different associations possessing various molecular size ranges, which can be separated from their integrated whole as nearly homogeneous and uniform species. In summary, the present study strongly speaks for the need to direct the research of natural dissolved and colloidal organic carbon more strongly toward a nanoscale study of supramolecular assemblies. More precise knowledge about the primary, secondary, and tertiary structure of dissolved DOM constituents has its essential function, e.g., for environmental protection and utilization of surface waters.

Chromatography, High Pressure Liquid↗

PubMed1996

Comparison of matrix vesicles derived from normal and osteoarthritic human articular cartilage.

Articular cartilage matrix vesicles (MVs) from normal human adult articular cartilage were examined for protein and enzyme content and biomineralizing capacity for comparison to MVs derived from human osteoarthritic (OA) cartilage. Femoral condylar and tibial plateau cartilage from each of 9 healthy donors ages 17-37 y was enzymatically digested and serially ultracentrifuged to pellet MV's at 3 x 10(6) g-min. MV protein content, nucleoside triphosphate pyrophospho hydrolase (NTPPPH) specific activity (SA) and capacity for 45Ca precipitation were determined. MV precipitated mineral was examined using Fourier transform infrared spectroscopy (FTIR). Normal human cartilage yields 50% less MV protein/g cartilage than OA cartilage (p < .01). Normal human articular MVs possess 30-70x higher NTPPPH SA than cell-free digest. Mean NTPPPH SAs of MVs derived from normal human cartilage are 3x higher than that of OA MVs (p < .05) and normal MV NTPPPH SA appears to decrease with age (p < .01). Normal human MVs support significantly higher calcium precipitation/mg MV protein in both ATP-dependent (p < .01) and -independent (p = .05) systems. The FTIR spectrum of MV mineral generated in the presence of ATP strongly resembles the standard spectrum for calcium pyrophosphate dihydrate (CPPD). The FTIR spectrum of MV mineral generated without ATP resembles that of carbonate-substituted apatite (AP). The fact that isolated MVs from normal cartilage generate pathologically relevant crystal phases in vitro implies that matrix integrity and substrate availability may be crucial factors in the control of pathologic biomineralization.

Adolescent↗

PubMed2006

Preparation of semi-interpenetrating polymer networks composed of chitosan and poloxamer.

Through semi-interpenetration of polymer networks with poloxamer, mechanical properties of chitosan (CS) sponge were increased for wound dressing application. Synthesis of poloxamer macromer was confirmed by proton nuclear magnetic resonance (1H NMR) spectra. Possible interactions between CS and poloxamer in semi-interpenetrating polymer networks (SIPNs), and changes in crystalline structures of both polymers were evaluated by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), respectively. Swelling behavior, thermal analysis, mechanical properties, and morphology of SIPNs were studied by thermal gravimetric analysis, differential scanning calorimetry (DSC), compressive modulus measurement, and scanning electron microscopy (SEM), respectively. Preparation of poloxamer macromer, and intermolecular hydrogen bonding between CS and poloxamer were confirmed by NMR and FTIR, respectively. Melting temperature of poloxamer in SIPNs decreased due to prevention of crystallization by incorporation of CS. Formation of SIPNs with poloxamer and increasing poloxamer content in CS/poloxamer SIPNs increased mechanical strength of CS sponge compared with CS/poloxamer blend. Formation of SIPNs with poloxamer remarkably increased water content of CS due to hydrophilicity of CS and poloxamer. These results suggest CS/poloxamer sponges prepared by SIPNs method have good possibility for wound dressing application owing to rapid water adsorption, high mechanical strength, and interconnected cross-sectional morphology of SIPNs.

Adsorption↗

PubMed2004

Effects of CaCl2 and MgCl2 on Fourier transform infrared spectra of lung cancer cells.

The cations Ca2+ and Mg2+ are two important factors in the growth and maintenance of living cells. The addition of Ca2+ to living cells can cause a change in the three-dimensional (3D) structure of calcium binding proteins. Therefore, we decided to study whether the addition of CaCl2 and MgCl2 to three in vitro growing lung cancer cell lines could cause changes that could be measured by Fourier Transform Infrared Spectroscopy. The addition of CaCl2 or MgCl2 to lung cancer cells caused an increase in absorbance of the trough at 1410 cm(-1). This translated into an inversion of the 1410/1395 cm(-1) ratio following the addition of CaCl2 or MgCl2 for all three lung cancer cell lines. Also, the amide I peak shifted from around 1631 cm(-1) to lower wavenumbers when CaCl2 or MgCl2 was added to cancer cells. Furthermore, the addition of these two substances caused a shift of the peak between 3290 and 3395 cm(-1). Finally, while the addition of CaCl2 to lung cancer cells was associated with an increased cell death, this was not the case following the addition of MgCl2. This would confirm that the changes seen in the spectra of all three cell lines are due to metabolic and ionic shifts rather than cell death.

Apoptosis↗

PubMed2003

Effect of hydrolyzed surface layer on the cytotoxicity and chemical resistance of a low fusing porcelain.

OBJECTIVE: The objectives of this study were to verify the formation of a hydrolyzed surface layer on Duceram LFC and to determine its effect on the cytotoxicity of the porcelain as measured by cellular activity and concentrations of leached ionic species. METHODS: Specimens were fabricated from dentin porcelain by a vibration blotting technique. Half of the specimens underwent accelerated aging by subjecting them to the standard test for hydrolytic resistance (ISO 6872). Fibroblast cell cultures were placed in direct contact with specimens. Cell viability was assessed using succinic dehydrogenase activity. Chemical resistance was determined by leaching specimens with a continuous flow of deionized water and measuring the concentrations of soluble ions in the leachates. Porcelain surface topography was examined using atomic force microscopy, and Fourier transform infrared spectroscopy was used to detect the composition of the surface layer. RESULTS: Hydrolyzation treatment created a smooth texture on the porcelain surfaces but did not result in a hydrolyzed surface layer with increased hydroxyl content. There was a decreased alkali ion content in the surface layer of hydrolyzed specimens. Mean cellular SDH activities for non-hydrolyzed and hydrolyzed porcelain were 75+/-7 and 80+/-5% of Teflon controls, respectively. Only sodium ions were present in significant concentrations in collected leachates. The sodium concentration decreased over the initial 4.5h of leaching. SIGNIFICANCE: The changes in surface layer texture and composition as the result of the aging treatment had little effect on the cytotoxicity and chemical resistance of Duceram LFC. The results suggest that Duceram LFC would pose no biocompatibility risk even after extended exposure to the oral environment. These data also provide baseline material properties to be used in future studies of the effects of porcelain additives.

3T3 Cells↗

PubMed2002

Ligand-induced conformational and structural dynamics changes in Escherichia coli cyclic AMP receptor protein.

Cyclic AMP receptor protein (CRP) regulates the expression of a large number of genes in E. coli. It is activated by cAMP binding, which leads to some yet undefined conformational changes. These changes do not involve significant redistribution of secondary structures. A potential mechanism of activation is a ligand-induced change in structural dynamics. Hence, the cAMP-mediated conformational and structural dynamics changes in the wild-type CRP were investigated using hydrogen-deuterium exchange and Fourier transform infrared spectroscopy. Upon cAMP binding, the two functional domains within the wild-type CRP undergo conformational and structural dynamics changes in two opposite directions. While the smaller DNA-binding domain becomes more flexible, the larger cAMP-binding domain shifts to a less dynamic conformation, evidenced by a faster and a slower amide H-D exchange, respectively. To a lesser extent, binding of cGMP, a nonfunctional analogue of cAMP, also stabilizes the cAMP-binding domain, but it fails to mimic the relaxation effect of cAMP on the DNA-binding domain. Despite changes in the conformation and structural dynamics, cAMP binding does not alter significantly the secondary structural composition of the wild-type CRP. The apparent difference between functional and nonfunctional analogues of cAMP is the ability of cAMP to effect an increase in the dynamic motions of the DNA binding domain.

Binding Sites↗

PubMed1998

Porcine cerebroside sulfate activator (saposin B) secondary structure: CD, FTIR, and NMR studies.

Cerebroside sulfate activator protein (CSAct or saposin B) is one of a group of heat stable, low-molecular-weight proteins that appear to share a common structural motif. These have been referred to as saposin-like proteins and are thought to share a multiple amphipathic helical barrel structure with a conserved pattern of disulfide linkages. Porcine kidney CSAct was prepared in high purity and consisted of three major glycosylated subforms. The protein was studied by physical-chemical methods and evaluated by various methods for structural prediction. All suggest that CSAct has high amounts of alpha-helical conformation and little if any beta-sheet. Circular dichroism (CD) studies indicate 45-50% helical conformation depending on buffer and temperature. There was only a moderate loss in helical content with increasing temperature and no indication of thermal denaturation. Fourier transform infrared spectroscopy (FTIR) measurements on deuterium hydrated self-films also indicated a predominantly helical structure. Helical axis orientation was investigated by both oriented CD and FTIR dichroism, which suggested that the helical axes were roughly parallel and oriented along the axis of the surface on which the self-films had been deposited. One-dimensional nuclear magnetic resonance spectra showed large chemical shift dispersion, indicating a defined tertiary structure with little variation between 6 and 85 degrees C. NOESY spectra failed to show the strong NOE cross peaks expected for a highly helical conformation. This may indicate short-term conformational flexibility within the helices or molecular aggregation at the high protein concentrations employed. These observations are consistent with the 3-4-helix bundle motif suggested for saposin-like proteins by various predictive algorithms.

Algorithms↗