Pub Date : 2009-03-18DOI: 10.2174/1874383800903010031
R. Rousseau
The Fundamental Algorithm between concentration (C i ) and intensity (R i ) in X-ray fluorescence analysis is deduced from Sherman's equation without any approximation. Its explicit expression is thus theoretically exact and it cor- rects completely for all matrix effects on the intensity R i emitted by the analyte i in a given specimen. This powerful algo- rithm combines the practical flexibility of the influence coefficient concept and the theoretical exactness of the Funda- mental-Parameters method. In association with its innovative calibration procedure, the Fundamental Algorithm can be applied to the analysis of any sample type and offers maximum accuracy, limited only by the quality of sample prepara- tion and the standards used.
{"title":"The Quest for a Fundamental Algorithm in X-Ray Fluorescence Analysis and Calibration","authors":"R. Rousseau","doi":"10.2174/1874383800903010031","DOIUrl":"https://doi.org/10.2174/1874383800903010031","url":null,"abstract":"The Fundamental Algorithm between concentration (C i ) and intensity (R i ) in X-ray fluorescence analysis is deduced from Sherman's equation without any approximation. Its explicit expression is thus theoretically exact and it cor- rects completely for all matrix effects on the intensity R i emitted by the analyte i in a given specimen. This powerful algo- rithm combines the practical flexibility of the influence coefficient concept and the theoretical exactness of the Funda- mental-Parameters method. In association with its innovative calibration procedure, the Fundamental Algorithm can be applied to the analysis of any sample type and offers maximum accuracy, limited only by the quality of sample prepara- tion and the standards used.","PeriodicalId":88758,"journal":{"name":"The open spectroscopy journal","volume":"66 1","pages":"31-42"},"PeriodicalIF":0.0,"publicationDate":"2009-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68069421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-03-13DOI: 10.2174/1874383800903010026
M. Kamel, R. Said, Aziza El-Beqqali, F. Bassyouni, M. Abdel-Rehim
Microextraction by packed sorbent (MEPS) was used to handle whole mice blood samples. MEPS was used as an online rapid sample-preparation method, followed by liquid chromatography with tandem mass spectrometry (LC- MS/MS). Cyclophosphamide in mice blood was used as a model compound. The new method reduced the handling time and the cost and could handle small volumes of whole blood samples (20 μL). The lower limit of quantification (LLOQ) was 0.1μg/mL. The accuracy of the quality-control (QC) samples ranged from 107 to 110 %. The within-day variation was within the range 2.0-7.0% (C.V.%) while the between-day variation was between 4.0 and 6.0% (C.V.%). The calibra- tion curve in whole blood was constructed within the concentration range 0.1-100 μg/mL. The coefficients of determina- tion (R 2 ) were > 0.99 (n = 3). The present method is rapid, reliable and accurate and may be used for therapeutic drug monitoring of cyclophosphamide in whole blood. The method was applied for preclinical study of cyclophosphamide in mice.
{"title":"On-Line Determination of Cyclophosphamide in Blood Samples Utilizing Microextraction by Packed Sorbent and Liquid Chromatography Tandem Mass Spectrometry (MEPS-LC-MS/MS)","authors":"M. Kamel, R. Said, Aziza El-Beqqali, F. Bassyouni, M. Abdel-Rehim","doi":"10.2174/1874383800903010026","DOIUrl":"https://doi.org/10.2174/1874383800903010026","url":null,"abstract":"Microextraction by packed sorbent (MEPS) was used to handle whole mice blood samples. MEPS was used as an online rapid sample-preparation method, followed by liquid chromatography with tandem mass spectrometry (LC- MS/MS). Cyclophosphamide in mice blood was used as a model compound. The new method reduced the handling time and the cost and could handle small volumes of whole blood samples (20 μL). The lower limit of quantification (LLOQ) was 0.1μg/mL. The accuracy of the quality-control (QC) samples ranged from 107 to 110 %. The within-day variation was within the range 2.0-7.0% (C.V.%) while the between-day variation was between 4.0 and 6.0% (C.V.%). The calibra- tion curve in whole blood was constructed within the concentration range 0.1-100 μg/mL. The coefficients of determina- tion (R 2 ) were > 0.99 (n = 3). The present method is rapid, reliable and accurate and may be used for therapeutic drug monitoring of cyclophosphamide in whole blood. The method was applied for preclinical study of cyclophosphamide in mice.","PeriodicalId":88758,"journal":{"name":"The open spectroscopy journal","volume":"3 1","pages":"26-30"},"PeriodicalIF":0.0,"publicationDate":"2009-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68069370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-02-13DOI: 10.2174/1874383800903010021
J. Szulejko, Sally Hall, M. Jackson, T. Solouki
Two common bacteria, Streptococcus pyogenes and Pseudomonas aeruginosa, were differentiated based on their volatile metabolic waste products. The bacteria were cultured in a closed system and the headspace above the culture medium were collected, preconcentrated, and analyzed using a gas chromatography Fourier transform ion cyclotron reso- nance mass spectrometer (GC/FT-ICR MS).
{"title":"Differentiation Between Pure Cultures of Streptococcus pyogenes and Pseudomonas aeruginosa by FT-ICR-MS Volatile Analysis","authors":"J. Szulejko, Sally Hall, M. Jackson, T. Solouki","doi":"10.2174/1874383800903010021","DOIUrl":"https://doi.org/10.2174/1874383800903010021","url":null,"abstract":"Two common bacteria, Streptococcus pyogenes and Pseudomonas aeruginosa, were differentiated based on their volatile metabolic waste products. The bacteria were cultured in a closed system and the headspace above the culture medium were collected, preconcentrated, and analyzed using a gas chromatography Fourier transform ion cyclotron reso- nance mass spectrometer (GC/FT-ICR MS).","PeriodicalId":88758,"journal":{"name":"The open spectroscopy journal","volume":"3 1","pages":"21-25"},"PeriodicalIF":0.0,"publicationDate":"2009-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68069358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-02-12DOI: 10.2174/1874383800903010009
S. Konorov, H. G. Schulze, C. Addison, C. Haynes, M. Blades, R. Turner
Base stacking plays an important role in excited state dynamics in polynucleotides. However, it is poorly un- derstood how stacking geometries influence the formation of and relaxation from excites states. Natural poly(dA)·poly(dT) adopts a B-form structure with extensive geometrical overlap between adjacent stacked adenines while the synthetic, locked ribose analogue (LNA), adopts the A-form structure where such overlap between adjacent adenines is reduced. We have used pump-probe transient absorption measurements on DNA and LNA, with excitation at 260 nm and absorption monitored at 440 and 260 nm, to examine the differences in excited state dynamics in B- and A-form con- formations. We observed slow decay times, both early and late stage, from the excited states of B-form and fast decay times from the excited states of analogous homopolymeric A-form structures. Within similar conformations, relaxation times are dependent on the number of stacked adenines as determined by either chain length or sequence. An increase in excited state lifetimes with increase in the number of stacked adenines shows that these excited states can be delocalized over several bases. Thus excited state lifetimes are highly dependent on how the bases are stacked. We conclude from our results that, for identical sequences, conformations that exhibit a high degree of adenine base overlap favor initial coop- erative excitation as well as subsequent evolution to delocalized excited states, but hinder the formation of out-of-plane geometries required for fast relaxation to the electronic ground state thus prolonging excited state lifetimes.
{"title":"Base Stacking Configuration is a Major Determinant of Excited State Dynamics in A. T DNA and LNA","authors":"S. Konorov, H. G. Schulze, C. Addison, C. Haynes, M. Blades, R. Turner","doi":"10.2174/1874383800903010009","DOIUrl":"https://doi.org/10.2174/1874383800903010009","url":null,"abstract":"Base stacking plays an important role in excited state dynamics in polynucleotides. However, it is poorly un- derstood how stacking geometries influence the formation of and relaxation from excites states. Natural poly(dA)·poly(dT) adopts a B-form structure with extensive geometrical overlap between adjacent stacked adenines while the synthetic, locked ribose analogue (LNA), adopts the A-form structure where such overlap between adjacent adenines is reduced. We have used pump-probe transient absorption measurements on DNA and LNA, with excitation at 260 nm and absorption monitored at 440 and 260 nm, to examine the differences in excited state dynamics in B- and A-form con- formations. We observed slow decay times, both early and late stage, from the excited states of B-form and fast decay times from the excited states of analogous homopolymeric A-form structures. Within similar conformations, relaxation times are dependent on the number of stacked adenines as determined by either chain length or sequence. An increase in excited state lifetimes with increase in the number of stacked adenines shows that these excited states can be delocalized over several bases. Thus excited state lifetimes are highly dependent on how the bases are stacked. We conclude from our results that, for identical sequences, conformations that exhibit a high degree of adenine base overlap favor initial coop- erative excitation as well as subsequent evolution to delocalized excited states, but hinder the formation of out-of-plane geometries required for fast relaxation to the electronic ground state thus prolonging excited state lifetimes.","PeriodicalId":88758,"journal":{"name":"The open spectroscopy journal","volume":"3 1","pages":"9-20"},"PeriodicalIF":0.0,"publicationDate":"2009-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68069306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-01-21DOI: 10.2174/1874383800903010001
R. Ganeev
Resonance-induced enhancement of the single harmonic generating in laser-produced plasmas allows achieving the microJoule energies for the coherent pulses in the extreme ultraviolet region using the moderate-intensity lasers. We review various approaches for improving the enhancement of single harmonic, which paves the way for a growth of har- monic yield in the short-wavelength range for various applications. enabled the overlap of these harmonics with the ionic transi- tions with strong oscillator strengths. Another approach for the tuning of harmonic wavelength based on the chirp varia- tions of driving radiation has been reported during gas HHG studies (15-17). Moreover, the tuning of harmonics and their "sharpness" were demonstrated using a combination of the external control of laser chirp and the intensity-induced variation of laser chirp inside a nonlinear medium (16, 17). In this mini-review, we discuss recent studies of the en- hancement of a single harmonic intensity in different parts of plateau in the case of plasma HHG. After brief overview of the experimental details, we analyze the giant single har- monic generation in indium plasma and other plasmas where the harmonic enhancement was reported. We also discuss the conditions of single harmonic enhancement at strong excita- tion of the plasma by femtosecond radiation and using the ultraviolet laser.
{"title":"Resonance-Induced Enhancement of the High-Order Harmonic Generation in Plasma","authors":"R. Ganeev","doi":"10.2174/1874383800903010001","DOIUrl":"https://doi.org/10.2174/1874383800903010001","url":null,"abstract":"Resonance-induced enhancement of the single harmonic generating in laser-produced plasmas allows achieving the microJoule energies for the coherent pulses in the extreme ultraviolet region using the moderate-intensity lasers. We review various approaches for improving the enhancement of single harmonic, which paves the way for a growth of har- monic yield in the short-wavelength range for various applications. enabled the overlap of these harmonics with the ionic transi- tions with strong oscillator strengths. Another approach for the tuning of harmonic wavelength based on the chirp varia- tions of driving radiation has been reported during gas HHG studies (15-17). Moreover, the tuning of harmonics and their \"sharpness\" were demonstrated using a combination of the external control of laser chirp and the intensity-induced variation of laser chirp inside a nonlinear medium (16, 17). In this mini-review, we discuss recent studies of the en- hancement of a single harmonic intensity in different parts of plateau in the case of plasma HHG. After brief overview of the experimental details, we analyze the giant single har- monic generation in indium plasma and other plasmas where the harmonic enhancement was reported. We also discuss the conditions of single harmonic enhancement at strong excita- tion of the plasma by femtosecond radiation and using the ultraviolet laser.","PeriodicalId":88758,"journal":{"name":"The open spectroscopy journal","volume":"3 1","pages":"1-8"},"PeriodicalIF":0.0,"publicationDate":"2009-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68069296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-01-02DOI: 10.2174/1874383800802010034
I. Matečko, Bjoern Burmann, K. Schweimer, H. Kalbacher, J. Einsiedel, P. Gmeiner, P. Rösch
E. coli heat stable enterotoxin STa is an agonist of the membrane guanylate cyclase C whose endogenous ligands are the peptide hormones guanylin and uroguanylin. Whereas these peptides contain only two disulfide bonds, STa is stabilized by one additional disulfide bridge. We chemically synthesized the enterotoxin STh that originates from the E. coli strain found in humans, and we determined its structure and its dynamics by nuclear magnetic resonance spec- troscopy and molecular dynamics calculations. Chemical synthesis clearly proved successful and resulted in the formation of the native disulfide bonds. The endogenous ligands guanylin and uroguanylin show the same general structural features and dynamics properties as the enterotoxin.
{"title":"Structural Characterisation of the E. coli Heat Stable Enterotoxin STh","authors":"I. Matečko, Bjoern Burmann, K. Schweimer, H. Kalbacher, J. Einsiedel, P. Gmeiner, P. Rösch","doi":"10.2174/1874383800802010034","DOIUrl":"https://doi.org/10.2174/1874383800802010034","url":null,"abstract":"E. coli heat stable enterotoxin STa is an agonist of the membrane guanylate cyclase C whose endogenous ligands are the peptide hormones guanylin and uroguanylin. Whereas these peptides contain only two disulfide bonds, STa is stabilized by one additional disulfide bridge. We chemically synthesized the enterotoxin STh that originates from the E. coli strain found in humans, and we determined its structure and its dynamics by nuclear magnetic resonance spec- troscopy and molecular dynamics calculations. Chemical synthesis clearly proved successful and resulted in the formation of the native disulfide bonds. The endogenous ligands guanylin and uroguanylin show the same general structural features and dynamics properties as the enterotoxin.","PeriodicalId":88758,"journal":{"name":"The open spectroscopy journal","volume":"2 1","pages":"34-39"},"PeriodicalIF":0.0,"publicationDate":"2009-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68069729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-01-02DOI: 10.2174/1874383800802010040
S. Gupta, Y. Ding
Carbon nanotubes are of great interest because of unique physical (mechanical, electrical, thermal, and chemical) properties. Especially their large elastic modulus and breaking strength make them highly attractive for their use as reinforced agents for traditional as well as conductive polymers forming a new class of multifunctional advanced carbon composites-nanocomposites. This is in addition to high electrical conductivity achieved through lower percolation thresholds for multitude of applications. Polyaniline (PANI) has a high potential due to its ease of synthesis, excellent environmental and thermal stability and reversible control of its electrical properties. A variant of PANI doped with DNNSA (dinonyl napththalene sulfonic acid) facilitates more promise by making it soluble and easily processable. In this work, DNNSA-PANI is used as a matrix for both the singleand multiwalled carbon nanotubes as nanoscale reinforced agents. The films were prepared with varying nanotube contents synthesized by spin-cast preceded by ultrasonic mixing of the constituents for a few hours. They were characterized using complementary analytical tools include scanning electron microscopy, atomic force microscopy, X-Ray diffraction, visible micro-Raman spectroscopy and room temperature dc electrical conductivity. These techniques reveal their morphology and microscopic structure and physical properties that help to establish process-microstructure-property relationship. The resulting nanocomposites possess enhanced or new sets of physical properties. However, because of occasional presence of inhomogeneities, the interfacial interactions and physical properties are ‘site-selective’ revealed using Raman spectroscopy ascribed to the charge transfer. The present work also discusses some of the findings in light of self-alignment of nanotubes in polymer matrix and their optical and electrical properties keeping in view of their applications ranging printable organic electronic and sensor devices, electrodes for fuel cell and high-energy density Li batteries, biosensing platform, space and naval uses.
{"title":"Self-Assembled Conductive Network of Carbon Nanotubes-Polyaniline as Potential Nanocomposites","authors":"S. Gupta, Y. Ding","doi":"10.2174/1874383800802010040","DOIUrl":"https://doi.org/10.2174/1874383800802010040","url":null,"abstract":"Carbon nanotubes are of great interest because of unique physical (mechanical, electrical, thermal, and chemical) properties. Especially their large elastic modulus and breaking strength make them highly attractive for their use as reinforced agents for traditional as well as conductive polymers forming a new class of multifunctional advanced carbon composites-nanocomposites. This is in addition to high electrical conductivity achieved through lower percolation thresholds for multitude of applications. Polyaniline (PANI) has a high potential due to its ease of synthesis, excellent environmental and thermal stability and reversible control of its electrical properties. A variant of PANI doped with DNNSA (dinonyl napththalene sulfonic acid) facilitates more promise by making it soluble and easily processable. In this work, DNNSA-PANI is used as a matrix for both the singleand multiwalled carbon nanotubes as nanoscale reinforced agents. The films were prepared with varying nanotube contents synthesized by spin-cast preceded by ultrasonic mixing of the constituents for a few hours. They were characterized using complementary analytical tools include scanning electron microscopy, atomic force microscopy, X-Ray diffraction, visible micro-Raman spectroscopy and room temperature dc electrical conductivity. These techniques reveal their morphology and microscopic structure and physical properties that help to establish process-microstructure-property relationship. The resulting nanocomposites possess enhanced or new sets of physical properties. However, because of occasional presence of inhomogeneities, the interfacial interactions and physical properties are ‘site-selective’ revealed using Raman spectroscopy ascribed to the charge transfer. The present work also discusses some of the findings in light of self-alignment of nanotubes in polymer matrix and their optical and electrical properties keeping in view of their applications ranging printable organic electronic and sensor devices, electrodes for fuel cell and high-energy density Li batteries, biosensing platform, space and naval uses.","PeriodicalId":88758,"journal":{"name":"The open spectroscopy journal","volume":"2 1","pages":"40-49"},"PeriodicalIF":0.0,"publicationDate":"2009-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68069745","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-01-01DOI: 10.2174/1874383800903010058
Mehmet Sen, Mark Herzik, John W Craft, Andrea L Creath, Sameer Agrawal, Wolfram Ruf, Glen B Legge
Tissue Factor (TF) is well known for its role during the activation of the coagulation pathway, but it is also critical for tumor biology and inflammation through protease activated receptor (PAR) 2 signaling. This signaling function is modulated by the successive phosphorylation of residues Ser253 and Ser258 within the TF cytoplasmic region (TFCR). This paper reports how we used NMR and spectroscopic methods to investigate the structural propensities of the unphosphorylated and phosphorylated forms of the TFCR. When unphosphorylated, the TFCR forms a local hydrophobic collapse around Trp254 and an electropositive patch from the membrane proximal basic block (Arg246-Lys247) to the conserved PKCalpha consensus residue Lys255. Phosphorylation of Ser253 alters the charge characteristics of this membrane proximal region, thereby strengthening the interaction between residue Ala248 and the Trp254 aromatic group. Phosphorylation of the Ser258-Pro259 motif destabilizes a turn at the C-terminus to form an extended polyproline helical motif. Our data suggests that by changing both its charge and local structural propensity, covalent modifications of the TFCR can potentially regulate its association with the cellular membrane and its signaling partners.
{"title":"Spectroscopic Characterization of Successive Phosphorylation of the Tissue Factor Cytoplasmic Region.","authors":"Mehmet Sen, Mark Herzik, John W Craft, Andrea L Creath, Sameer Agrawal, Wolfram Ruf, Glen B Legge","doi":"10.2174/1874383800903010058","DOIUrl":"https://doi.org/10.2174/1874383800903010058","url":null,"abstract":"<p><p>Tissue Factor (TF) is well known for its role during the activation of the coagulation pathway, but it is also critical for tumor biology and inflammation through protease activated receptor (PAR) 2 signaling. This signaling function is modulated by the successive phosphorylation of residues Ser253 and Ser258 within the TF cytoplasmic region (TFCR). This paper reports how we used NMR and spectroscopic methods to investigate the structural propensities of the unphosphorylated and phosphorylated forms of the TFCR. When unphosphorylated, the TFCR forms a local hydrophobic collapse around Trp254 and an electropositive patch from the membrane proximal basic block (Arg246-Lys247) to the conserved PKCalpha consensus residue Lys255. Phosphorylation of Ser253 alters the charge characteristics of this membrane proximal region, thereby strengthening the interaction between residue Ala248 and the Trp254 aromatic group. Phosphorylation of the Ser258-Pro259 motif destabilizes a turn at the C-terminus to form an extended polyproline helical motif. Our data suggests that by changing both its charge and local structural propensity, covalent modifications of the TFCR can potentially regulate its association with the cellular membrane and its signaling partners.</p>","PeriodicalId":88758,"journal":{"name":"The open spectroscopy journal","volume":"3 ","pages":"58-64"},"PeriodicalIF":0.0,"publicationDate":"2009-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2805860/pdf/nihms137543.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"28648432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-06-21DOI: 10.2174/1874383800802010029
G. Kummerlöwe, F. Halbach, B. Laufer, B. Luy
Residual dipolar couplings (RDCs) are of great interest for the structure determination of biomacromolecules as well as of organic molecules like synthetic or natural products. Their accurate measurement requires a proper degree of alignment for the molecule under investigation. As has been shown recently, a stretching device based on a flexible sili- cone rubber tube provides an easy, rapid, and reversible variation of alignment strength. We show in this article that such an apparatus is not limited to gelatin, but can also be used with covalently cross-linked hydrogels and even gels with polar organic solvents like DMSO. Using sucrose and a cyclic hexapeptide, we were able to demonstrate that the approximately linear relation of alignment with the extension factor of the stretched gel allows the measurement of RDCs with high pre- cision if corresponding spectra are acquired at various alignment strengths. The method seems to be widely applicable to the structure determination of molecules of arbitrary size using standard 5 mm NMR equipment. For verification of the alignment properties of the stretch- ing apparatus, we prepared a 40% (w/v) sample of porcine gelatin with an approximate Bloomgrade of 250 dissolved at 50°C in D2O. As a solute molecule for measuring RDCs we added 43 mg of sucrose to a final concentration of approxi- mately 500 mM. Gelatin is a special gel which can be re- casted inside the rubber tube by a simple heating and recool- ing cycle, as it is cross-linked via hydrogen bonds only. In order to test how far the apparatus is applicable to conven- tional polymer gels with covalent cross-linking, we prepared several gel samples using published protocols with gel di- ameters adjusted to accomodate for the dimensions of the stretching apparatus. The results presented in this article were obtained using the following gel preparations: The poly(acrylamide) (PAA) gel was prepared from a solution of 8.55% (w/v) acrylamide and 0.45% (w/v) N,N'- methylenebis(acrylamide) with 0.1% (w/v) ammonium per- sulfate and 0.1% (v/v) N,N,N',N'-tetramethylethylendiamin for cross-linking (5). Radical polymerization was allowed for 1 h within glass tubes of 2.4 mm inner diameter. Gels were washed three times with water to remove free acrylamide before they were dried at room temperature.
{"title":"Precise Measurement of RDCs in Water and DMSO Based Gels Using a Silicone Rubber Tube for Tunable Stretching","authors":"G. Kummerlöwe, F. Halbach, B. Laufer, B. Luy","doi":"10.2174/1874383800802010029","DOIUrl":"https://doi.org/10.2174/1874383800802010029","url":null,"abstract":"Residual dipolar couplings (RDCs) are of great interest for the structure determination of biomacromolecules as well as of organic molecules like synthetic or natural products. Their accurate measurement requires a proper degree of alignment for the molecule under investigation. As has been shown recently, a stretching device based on a flexible sili- cone rubber tube provides an easy, rapid, and reversible variation of alignment strength. We show in this article that such an apparatus is not limited to gelatin, but can also be used with covalently cross-linked hydrogels and even gels with polar organic solvents like DMSO. Using sucrose and a cyclic hexapeptide, we were able to demonstrate that the approximately linear relation of alignment with the extension factor of the stretched gel allows the measurement of RDCs with high pre- cision if corresponding spectra are acquired at various alignment strengths. The method seems to be widely applicable to the structure determination of molecules of arbitrary size using standard 5 mm NMR equipment. For verification of the alignment properties of the stretch- ing apparatus, we prepared a 40% (w/v) sample of porcine gelatin with an approximate Bloomgrade of 250 dissolved at 50°C in D2O. As a solute molecule for measuring RDCs we added 43 mg of sucrose to a final concentration of approxi- mately 500 mM. Gelatin is a special gel which can be re- casted inside the rubber tube by a simple heating and recool- ing cycle, as it is cross-linked via hydrogen bonds only. In order to test how far the apparatus is applicable to conven- tional polymer gels with covalent cross-linking, we prepared several gel samples using published protocols with gel di- ameters adjusted to accomodate for the dimensions of the stretching apparatus. The results presented in this article were obtained using the following gel preparations: The poly(acrylamide) (PAA) gel was prepared from a solution of 8.55% (w/v) acrylamide and 0.45% (w/v) N,N'- methylenebis(acrylamide) with 0.1% (w/v) ammonium per- sulfate and 0.1% (v/v) N,N,N',N'-tetramethylethylendiamin for cross-linking (5). Radical polymerization was allowed for 1 h within glass tubes of 2.4 mm inner diameter. Gels were washed three times with water to remove free acrylamide before they were dried at room temperature.","PeriodicalId":88758,"journal":{"name":"The open spectroscopy journal","volume":"2 1","pages":"29-33"},"PeriodicalIF":0.0,"publicationDate":"2008-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68069663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-06-12DOI: 10.2174/1874383800802010019
H. Hammud, Fawzy A. El Yazbib, M. E. Mahrous, G. Sonji, N. Sonji
Spectrofluorimetric and high performance liquid chromatographic methods have been developed for the accu- rate and sensitive determination of Aspirin in mixture with Dipyridamole and in presence of its degradation product (Sali- cylic acid). The spectrofluorimetric method was based on the use of the first and second derivatives of the ratio of the emission spectra with a zero-crossing technique. The ratio spectra were obtained by dividing the emission spectrum of the ternary mixture by that of one of the components. The other components were quantified from their respective calibration graphs treated similarly. The proposed RP-HPLC method utilized an Adsorbosil C8, 10 � m, 250mmx4.6mm i.d. column, at ambient temperature, optimum mobile phase consisted of water-acetonitrile-ortho-phosphoric acid (65:35:2 v/v/v), with flow rate monitored at 1.5 ml/min, and UV detection at 250 nm. The total chromatographic time per sample was about 6 min with dipyridamole, aspirin and salicylic acid eluting at retention times 2.2, 3.8 and 4.6 min, respectively. Evaluation of linearity, accuracy, precision, selectivity and sensitivity of the methods produced satisfactory results. The objective of this work was to introduce new analytical methods for this ternary mixture, as the literature reveals only one method of analysis. The proposed methods were able to quantify Aspirin, Dipyridamole and Salicylic acid, irrespec- tive of the percentage of the latter in sample; and have been successfully applied to the commercial pharmaceutical formu- lations without any interference of excipients.
采用荧光光谱法和高效液相色谱法对阿司匹林与双嘧达莫的混合物及其降解产物(沙利环酸)进行了准确、灵敏的测定。荧光光谱法是基于利用零交叉技术的发射光谱比值的一阶导数和二阶导数。比值光谱由三元混合物的发射光谱除以其中一种组分的发射光谱得到。其他成分从各自的校准图中进行定量处理。反相高效液相色谱(RP-HPLC)色谱柱为C8, 10 μ m, 250mmx4.6mm，室温下，最佳流动相为水-乙腈-正磷酸(65:35:2 v/v/v)，流速为1.5 ml/min，检测波长为250 nm。每个样品的总色谱时间约为6 min，双嘧达莫、阿司匹林和水杨酸的洗脱时间分别为2.2、3.8和4.6 min。对方法的线性度、准确度、精密度、选择性和灵敏度进行了满意的评价。这项工作的目的是为这种三元混合物介绍新的分析方法，因为文献显示只有一种分析方法。所提出的方法能够定量测定阿司匹林、双嘧达莫和水杨酸，而不考虑后者在样品中的百分比;并已成功应用于商业制剂中，不受辅料的干扰。
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