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Research paper thumbnail of Control of Poorly Soluble Drug Dissolution in Conditions Simulating the Gastrointestinal Tract Flow. 2. Cocompression of Drugs with Buffers

Journal of Pharmaceutical Sciences, Apr 1, 1997

The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the prop... more The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the properties and flow dynamics of the liquid medium surrounding the tablet, as well as by the chemical nature of the drug. In this study, naproxen was used as a poorly soluble model drug. The dissolution medium was buffered with acetate, citrate, or phosphate buffer of varied concentrations and pH. GI flow conditions around a stationary tablet were simulated in a laminar flow device by anchoring the tablet on the floor of its channel having a rectangular cross section. Fresh, buffered solution was passed across the tablet and the effluent was collected for analysis and calculation of the dissolution rate. The dissolution rate was found to vary nonlinearly with the exposed tablet height, reaching a maximum at a tablet height approximately half the channel height. This maximum rate was attributed to an optimal combination of (1) eddy mixing and local turbulence generated by the flow impingement on the bluff object (tablet) and (2) the exposed tablet surface area available for dissolution. This effect was further confirmed by using dye-enhanced visual analysis of flow patterns at varied flow rates and exposed tablet heights. Elevation of the tablet to approximately the channel half-height significantly magnified the dissolution rate increase observed on exposure to buffered medium. Thus, tablet height and exposed surface area are major factors in determining dissolution rate, especially in conditions where the dissolving species reacts with the solvent. These results suggest that standard in vitro dissolution rate methods do not qualitatively indicate incremental changes in rate with altered tablet geometry or dissolution medium.

Research paper thumbnail of Control of Poorly Soluble Drug Dissolution in Conditions Simulating the Gastrointestinal Tract Flow. 1. Effect of Tablet Geometry in Buffered Medium

Journal of Pharmaceutical Sciences, Mar 1, 1996

The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the prop... more The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the properties and flow dynamics of the liquid medium surrounding the tablet, as well as by the chemical nature of the drug. In this study, naproxen was used as a poorly soluble model drug. The dissolution medium was buffered with acetate, citrate, or phosphate buffer of varied concentrations and pH. GI flow conditions around a stationary tablet were simulated in a laminar flow device by anchoring the tablet on the floor of its channel having a rectangular cross section. Fresh, buffered solution was passed across the tablet and the effluent was collected for analysis and calculation of the dissolution rate. The dissolution rate was found to vary nonlinearly with the exposed tablet height, reaching a maximum at a tablet height approximately half the channel height. This maximum rate was attributed to an optimal combination of (1) eddy mixing and local turbulence generated by the flow impingement on the bluff object (tablet) and (2) the exposed tablet surface area available for dissolution. This effect was further confirmed by using dye-enhanced visual analysis of flow patterns at varied flow rates and exposed tablet heights. Elevation of the tablet to approximately the channel half-height significantly magnified the dissolution rate increase observed on exposure to buffered medium. Thus, tablet height and exposed surface area are major factors in determining dissolution rate, especially in conditions where the dissolving species reacts with the solvent. These results suggest that standard in vitro dissolution rate methods do not qualitatively indicate incremental changes in rate with altered tablet geometry or dissolution medium.

Research paper thumbnail of Global Trends in Continuing Professional Development for Engineers

Research paper thumbnail of Re-engineering the Operations and Executing the Organizational Strategy Based on 4P’s in Redesigning Continuing Education Organizations

Research paper thumbnail of Preparing Engineers for Lifelong Learning in the Era of Industry 4.0

2021 World Engineering Education Forum/Global Engineering Deans Council (WEEF/GEDC)

Research paper thumbnail of Solution stability of linear vs. cyclic RGD peptides

Journal of Peptide Research, 1999

Research paper thumbnail of Global Trends in the contribution of University Lifelong Learning in shaping the labour markets and its applicability to EU – An IACEE Perspective

eucen Studies eJournal of University Lifelong Learning

Research paper thumbnail of Developing a Successful Framework for Online Delivery of Non-credit Engineering Short Courses to Global Aerospace Professionals

2012 ASEE Annual Conference & Exposition Proceedings

Research paper thumbnail of Building Industry-Academia Partnerships that Foster Organizational Learning Models

2014 ASEE Annual Conference & Exposition Proceedings

Research paper thumbnail of Building and Sustaining

2013 ASEE Annual Conference & Exposition Proceedings

Research paper thumbnail of Sustaining Successful Continuing Professional Engineering Education Programs by Systematic Assessment of the Key Performance Results

2013 ASEE Annual Conference & Exposition Proceedings

Research paper thumbnail of Establishing a Sustainable Business Model for a Continuing Aerospace Engineering Program

Proceedings of the 12th World Conference on Continuing Engineering Education, 2010

Research paper thumbnail of The aqueous conformation of cyclo(1,6)Ac-Cys-Arg-Gly-Asp-Phe-Pen-NH2

International Journal of Peptide and Protein Research, 1994

RGD peptides are known as important ligands for integrin receptors in the cell adhesion process. ... more RGD peptides are known as important ligands for integrin receptors in the cell adhesion process. The selectivity of RGD peptides for a certain integrin receptor is partly dependent on the RGD conformation and the residues surrounding the RGD sequence. This paper investigates the effect of the addition of a phenylalanine residue on the RGD conformation in cyclo(1,6)Ac-Cys-Arg-Gly-Asp-Phe-Pen-NH2 (1) as compared to the previously studied cyclo(1,5)Ac-Pen-Arg-Gly-Asp-Cys-NH2 (2). The conformational study of peptide 1 was done in aqueous solution using nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics simulations. This work will increase the understanding of the flanking residue's effect in RGD peptides.

Research paper thumbnail of Control of poorly soluble drug dissolution in conditions simulating the gastrointestinal tract flow. 2. Cocompression of drugs with buffers

Journal of Pharmaceutical Sciences, 1997

The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the prop... more The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the properties and flow dynamics of the liquid medium surrounding the tablet, as well as by the chemical nature of the drug. In this study, naproxen was used as a poorly soluble model drug. The dissolution medium was buffered with acetate, citrate, or phosphate buffer of varied concentrations and pH. GI flow conditions around a stationary tablet were simulated in a laminar flow device by anchoring the tablet on the floor of its channel having a rectangular cross section. Fresh, buffered solution was passed across the tablet and the effluent was collected for analysis and calculation of the dissolution rate. The dissolution rate was found to vary nonlinearly with the exposed tablet height, reaching a maximum at a tablet height approximately half the channel height. This maximum rate was attributed to an optimal combination of (1) eddy mixing and local turbulence generated by the flow impingement on the bluff object (tablet) and (2) the exposed tablet surface area available for dissolution. This effect was further confirmed by using dye-enhanced visual analysis of flow patterns at varied flow rates and exposed tablet heights. Elevation of the tablet to approximately the channel half-height significantly magnified the dissolution rate increase observed on exposure to buffered medium. Thus, tablet height and exposed surface area are major factors in determining dissolution rate, especially in conditions where the dissolving species reacts with the solvent. These results suggest that standard in vitro dissolution rate methods do not qualitatively indicate incremental changes in rate with altered tablet geometry or dissolution medium.

Research paper thumbnail of Solution Structure of a Cyclic RGD Peptide That Inhibits Platelet Aggregation

Journal of Biomolecular Structure and Dynamics, 1996

Research paper thumbnail of Conformational analysis of cyclo(2,9)-Ac-QCRSVEGSCG-OH from the C-terminal loop of human growth hormone

The Journal of Peptide Research, 2009

A 10 amino acid residue cyclic peptide, cyclo(2,9)-Ac-Glnl-Cys2-Arg3-Ser4-Val5-Glu6-Gly7-Ser8-Cys... more A 10 amino acid residue cyclic peptide, cyclo(2,9)-Ac-Glnl-Cys2-Arg3-Ser4-Val5-Glu6-Gly7-Ser8-Cys9-Glyl0, from the C-terminal region of human growth hormone (hGH) was synthesized and studied by 2D proton NMR and molecular dynamics (MD) simulations. The solubility of the peptide was low in water; hence, NMR studies were done in two solvent mixtures, water and deuterated dimethyl sulfoxide. NOE-constrained molecular dynamics and MD simulations resulted in major and minor conformers in solution. The major conformer has a type I p-turn at Glnl-Cys2-Arg3-Ser4 and a loop structure around Glu6-Gly7-Ser8. Comparison of the conformation of this peptide with the peptide fragment 181-190 in the intact hGH protein X-ray crystal structure indicated that the synthetic peptide retains some structural similarity to the intact protein. Since the C-terminal region is important in binding the hCH protein to its receptor, the conformation of the synthetic peptide could be useful in understanding the binding mechanism. 0 Munksgaard 1997.

Research paper thumbnail of Conformational study of cyclo(1,5)-Ac-Pen-Arg-Gly-Asp-Cys-NH2 in water by NMR and molecular dynamics

Biochemical and Biophysical Research Communications, 1992

Cyclo(l,S)-Ac-Pen-Arg-Gly-Asp-Cys-NH2 (3) is a potent inhibitor of platelet aggregation. Nuclear ... more Cyclo(l,S)-Ac-Pen-Arg-Gly-Asp-Cys-NH2 (3) is a potent inhibitor of platelet aggregation. Nuclear magnetic resonance (NMR) and restrained molecular dynamics were used to study the conformations of 3. Elucidation of RGD conformations in 3 will increase the understanding of interaction between the RGD-sequence with GPIIb/IIIa.

Research paper thumbnail of Conformational analysis of cyclo (2, 9)‐Ac‐QCRSVEGSCG‐OH from the C‐terminal loop of human growth hormone

The Journal of …, 1997

A 10 amino acid residue cyclic peptide, cyclo(2,9)-Ac-Glnl-Cys2-Arg3-Ser4-Val5-Glu6-Gly7-Ser8-Cys... more A 10 amino acid residue cyclic peptide, cyclo(2,9)-Ac-Glnl-Cys2-Arg3-Ser4-Val5-Glu6-Gly7-Ser8-Cys9-Glyl0, from the C-terminal region of human growth hormone (hGH) was synthesized and studied by 2D proton NMR and molecular dynamics (MD) simulations. The solubility of the peptide was low in water; hence, NMR studies were done in two solvent mixtures, water and deuterated dimethyl sulfoxide. NOE-constrained molecular dynamics and MD simulations resulted in major and minor conformers in solution. The major conformer has a type I p-turn at Glnl-Cys2-Arg3-Ser4 and a loop structure around Glu6-Gly7-Ser8. Comparison of the conformation of this peptide with the peptide fragment 181-190 in the intact hGH protein X-ray crystal structure indicated that the synthetic peptide retains some structural similarity to the intact protein. Since the C-terminal region is important in binding the hCH protein to its receptor, the conformation of the synthetic peptide could be useful in understanding the binding mechanism. 0 Munksgaard 1997.

Research paper thumbnail of The aqueous conformation of cyclo (1, 6) Ac‐Cys‐Arg‐Gly‐Asp‐Phe‐Pen‐NH2

… Journal of Peptide …, 1994

RGD peptides are known as important ligands for integrin receptors in the cell adhesion process. ... more RGD peptides are known as important ligands for integrin receptors in the cell adhesion process. The selectivity of RGD peptides for a certain integrin receptor is partly dependent on the RGD conformation and the residues surrounding the RGD sequence. This paper investigates the effect of the addition of a phenylalanine residue on the RGD conformation in cyclo(1,6)Ac-Cys-Arg-Gly-Asp-Phe-Pen-NH2 (1) as compared to the previously studied cyclo(1,5)Ac-Pen-Arg-Gly-Asp-Cys-NH2 (2). The conformational study of peptide 1 was done in aqueous solution using nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics simulations. This work will increase the understanding of the flanking residue's effect in RGD peptides.

Research paper thumbnail of Control of poorly soluble drug dissolution in conditions simulating the gastrointestinal tract flow. 2. Cocompression of drugs with buffers

Journal of pharmaceutical …, 1997

The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the prop... more The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the properties and flow dynamics of the liquid medium surrounding the tablet, as well as by the chemical nature of the drug. In this study, naproxen was used as a poorly soluble model drug. The dissolution medium was buffered with acetate, citrate, or phosphate buffer of varied concentrations and pH. GI flow conditions around a stationary tablet were simulated in a laminar flow device by anchoring the tablet on the floor of its channel having a rectangular cross section. Fresh, buffered solution was passed across the tablet and the effluent was collected for analysis and calculation of the dissolution rate. The dissolution rate was found to vary nonlinearly with the exposed tablet height, reaching a maximum at a tablet height approximately half the channel height. This maximum rate was attributed to an optimal combination of (1) eddy mixing and local turbulence generated by the flow impingement on the bluff object (tablet) and (2) the exposed tablet surface area available for dissolution. This effect was further confirmed by using dye-enhanced visual analysis of flow patterns at varied flow rates and exposed tablet heights. Elevation of the tablet to approximately the channel half-height significantly magnified the dissolution rate increase observed on exposure to buffered medium. Thus, tablet height and exposed surface area are major factors in determining dissolution rate, especially in conditions where the dissolving species reacts with the solvent. These results suggest that standard in vitro dissolution rate methods do not qualitatively indicate incremental changes in rate with altered tablet geometry or dissolution medium.

Research paper thumbnail of Control of Poorly Soluble Drug Dissolution in Conditions Simulating the Gastrointestinal Tract Flow. 2. Cocompression of Drugs with Buffers

Journal of Pharmaceutical Sciences, Apr 1, 1997

The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the prop... more The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the properties and flow dynamics of the liquid medium surrounding the tablet, as well as by the chemical nature of the drug. In this study, naproxen was used as a poorly soluble model drug. The dissolution medium was buffered with acetate, citrate, or phosphate buffer of varied concentrations and pH. GI flow conditions around a stationary tablet were simulated in a laminar flow device by anchoring the tablet on the floor of its channel having a rectangular cross section. Fresh, buffered solution was passed across the tablet and the effluent was collected for analysis and calculation of the dissolution rate. The dissolution rate was found to vary nonlinearly with the exposed tablet height, reaching a maximum at a tablet height approximately half the channel height. This maximum rate was attributed to an optimal combination of (1) eddy mixing and local turbulence generated by the flow impingement on the bluff object (tablet) and (2) the exposed tablet surface area available for dissolution. This effect was further confirmed by using dye-enhanced visual analysis of flow patterns at varied flow rates and exposed tablet heights. Elevation of the tablet to approximately the channel half-height significantly magnified the dissolution rate increase observed on exposure to buffered medium. Thus, tablet height and exposed surface area are major factors in determining dissolution rate, especially in conditions where the dissolving species reacts with the solvent. These results suggest that standard in vitro dissolution rate methods do not qualitatively indicate incremental changes in rate with altered tablet geometry or dissolution medium.

Research paper thumbnail of Control of Poorly Soluble Drug Dissolution in Conditions Simulating the Gastrointestinal Tract Flow. 1. Effect of Tablet Geometry in Buffered Medium

Journal of Pharmaceutical Sciences, Mar 1, 1996

The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the prop... more The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the properties and flow dynamics of the liquid medium surrounding the tablet, as well as by the chemical nature of the drug. In this study, naproxen was used as a poorly soluble model drug. The dissolution medium was buffered with acetate, citrate, or phosphate buffer of varied concentrations and pH. GI flow conditions around a stationary tablet were simulated in a laminar flow device by anchoring the tablet on the floor of its channel having a rectangular cross section. Fresh, buffered solution was passed across the tablet and the effluent was collected for analysis and calculation of the dissolution rate. The dissolution rate was found to vary nonlinearly with the exposed tablet height, reaching a maximum at a tablet height approximately half the channel height. This maximum rate was attributed to an optimal combination of (1) eddy mixing and local turbulence generated by the flow impingement on the bluff object (tablet) and (2) the exposed tablet surface area available for dissolution. This effect was further confirmed by using dye-enhanced visual analysis of flow patterns at varied flow rates and exposed tablet heights. Elevation of the tablet to approximately the channel half-height significantly magnified the dissolution rate increase observed on exposure to buffered medium. Thus, tablet height and exposed surface area are major factors in determining dissolution rate, especially in conditions where the dissolving species reacts with the solvent. These results suggest that standard in vitro dissolution rate methods do not qualitatively indicate incremental changes in rate with altered tablet geometry or dissolution medium.

Research paper thumbnail of Global Trends in Continuing Professional Development for Engineers

Research paper thumbnail of Re-engineering the Operations and Executing the Organizational Strategy Based on 4P’s in Redesigning Continuing Education Organizations

Research paper thumbnail of Preparing Engineers for Lifelong Learning in the Era of Industry 4.0

2021 World Engineering Education Forum/Global Engineering Deans Council (WEEF/GEDC)

Research paper thumbnail of Solution stability of linear vs. cyclic RGD peptides

Journal of Peptide Research, 1999

Research paper thumbnail of Global Trends in the contribution of University Lifelong Learning in shaping the labour markets and its applicability to EU – An IACEE Perspective

eucen Studies eJournal of University Lifelong Learning

Research paper thumbnail of Developing a Successful Framework for Online Delivery of Non-credit Engineering Short Courses to Global Aerospace Professionals

2012 ASEE Annual Conference & Exposition Proceedings

Research paper thumbnail of Building Industry-Academia Partnerships that Foster Organizational Learning Models

2014 ASEE Annual Conference & Exposition Proceedings

Research paper thumbnail of Building and Sustaining

2013 ASEE Annual Conference & Exposition Proceedings

Research paper thumbnail of Sustaining Successful Continuing Professional Engineering Education Programs by Systematic Assessment of the Key Performance Results

2013 ASEE Annual Conference & Exposition Proceedings

Research paper thumbnail of Establishing a Sustainable Business Model for a Continuing Aerospace Engineering Program

Proceedings of the 12th World Conference on Continuing Engineering Education, 2010

Research paper thumbnail of The aqueous conformation of cyclo(1,6)Ac-Cys-Arg-Gly-Asp-Phe-Pen-NH2

International Journal of Peptide and Protein Research, 1994

RGD peptides are known as important ligands for integrin receptors in the cell adhesion process. ... more RGD peptides are known as important ligands for integrin receptors in the cell adhesion process. The selectivity of RGD peptides for a certain integrin receptor is partly dependent on the RGD conformation and the residues surrounding the RGD sequence. This paper investigates the effect of the addition of a phenylalanine residue on the RGD conformation in cyclo(1,6)Ac-Cys-Arg-Gly-Asp-Phe-Pen-NH2 (1) as compared to the previously studied cyclo(1,5)Ac-Pen-Arg-Gly-Asp-Cys-NH2 (2). The conformational study of peptide 1 was done in aqueous solution using nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics simulations. This work will increase the understanding of the flanking residue's effect in RGD peptides.

Research paper thumbnail of Control of poorly soluble drug dissolution in conditions simulating the gastrointestinal tract flow. 2. Cocompression of drugs with buffers

Journal of Pharmaceutical Sciences, 1997

The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the prop... more The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the properties and flow dynamics of the liquid medium surrounding the tablet, as well as by the chemical nature of the drug. In this study, naproxen was used as a poorly soluble model drug. The dissolution medium was buffered with acetate, citrate, or phosphate buffer of varied concentrations and pH. GI flow conditions around a stationary tablet were simulated in a laminar flow device by anchoring the tablet on the floor of its channel having a rectangular cross section. Fresh, buffered solution was passed across the tablet and the effluent was collected for analysis and calculation of the dissolution rate. The dissolution rate was found to vary nonlinearly with the exposed tablet height, reaching a maximum at a tablet height approximately half the channel height. This maximum rate was attributed to an optimal combination of (1) eddy mixing and local turbulence generated by the flow impingement on the bluff object (tablet) and (2) the exposed tablet surface area available for dissolution. This effect was further confirmed by using dye-enhanced visual analysis of flow patterns at varied flow rates and exposed tablet heights. Elevation of the tablet to approximately the channel half-height significantly magnified the dissolution rate increase observed on exposure to buffered medium. Thus, tablet height and exposed surface area are major factors in determining dissolution rate, especially in conditions where the dissolving species reacts with the solvent. These results suggest that standard in vitro dissolution rate methods do not qualitatively indicate incremental changes in rate with altered tablet geometry or dissolution medium.

Research paper thumbnail of Solution Structure of a Cyclic RGD Peptide That Inhibits Platelet Aggregation

Journal of Biomolecular Structure and Dynamics, 1996

Research paper thumbnail of Conformational analysis of cyclo(2,9)-Ac-QCRSVEGSCG-OH from the C-terminal loop of human growth hormone

The Journal of Peptide Research, 2009

A 10 amino acid residue cyclic peptide, cyclo(2,9)-Ac-Glnl-Cys2-Arg3-Ser4-Val5-Glu6-Gly7-Ser8-Cys... more A 10 amino acid residue cyclic peptide, cyclo(2,9)-Ac-Glnl-Cys2-Arg3-Ser4-Val5-Glu6-Gly7-Ser8-Cys9-Glyl0, from the C-terminal region of human growth hormone (hGH) was synthesized and studied by 2D proton NMR and molecular dynamics (MD) simulations. The solubility of the peptide was low in water; hence, NMR studies were done in two solvent mixtures, water and deuterated dimethyl sulfoxide. NOE-constrained molecular dynamics and MD simulations resulted in major and minor conformers in solution. The major conformer has a type I p-turn at Glnl-Cys2-Arg3-Ser4 and a loop structure around Glu6-Gly7-Ser8. Comparison of the conformation of this peptide with the peptide fragment 181-190 in the intact hGH protein X-ray crystal structure indicated that the synthetic peptide retains some structural similarity to the intact protein. Since the C-terminal region is important in binding the hCH protein to its receptor, the conformation of the synthetic peptide could be useful in understanding the binding mechanism. 0 Munksgaard 1997.

Research paper thumbnail of Conformational study of cyclo(1,5)-Ac-Pen-Arg-Gly-Asp-Cys-NH2 in water by NMR and molecular dynamics

Biochemical and Biophysical Research Communications, 1992

Cyclo(l,S)-Ac-Pen-Arg-Gly-Asp-Cys-NH2 (3) is a potent inhibitor of platelet aggregation. Nuclear ... more Cyclo(l,S)-Ac-Pen-Arg-Gly-Asp-Cys-NH2 (3) is a potent inhibitor of platelet aggregation. Nuclear magnetic resonance (NMR) and restrained molecular dynamics were used to study the conformations of 3. Elucidation of RGD conformations in 3 will increase the understanding of interaction between the RGD-sequence with GPIIb/IIIa.

Research paper thumbnail of Conformational analysis of cyclo (2, 9)‐Ac‐QCRSVEGSCG‐OH from the C‐terminal loop of human growth hormone

The Journal of …, 1997

A 10 amino acid residue cyclic peptide, cyclo(2,9)-Ac-Glnl-Cys2-Arg3-Ser4-Val5-Glu6-Gly7-Ser8-Cys... more A 10 amino acid residue cyclic peptide, cyclo(2,9)-Ac-Glnl-Cys2-Arg3-Ser4-Val5-Glu6-Gly7-Ser8-Cys9-Glyl0, from the C-terminal region of human growth hormone (hGH) was synthesized and studied by 2D proton NMR and molecular dynamics (MD) simulations. The solubility of the peptide was low in water; hence, NMR studies were done in two solvent mixtures, water and deuterated dimethyl sulfoxide. NOE-constrained molecular dynamics and MD simulations resulted in major and minor conformers in solution. The major conformer has a type I p-turn at Glnl-Cys2-Arg3-Ser4 and a loop structure around Glu6-Gly7-Ser8. Comparison of the conformation of this peptide with the peptide fragment 181-190 in the intact hGH protein X-ray crystal structure indicated that the synthetic peptide retains some structural similarity to the intact protein. Since the C-terminal region is important in binding the hCH protein to its receptor, the conformation of the synthetic peptide could be useful in understanding the binding mechanism. 0 Munksgaard 1997.

Research paper thumbnail of The aqueous conformation of cyclo (1, 6) Ac‐Cys‐Arg‐Gly‐Asp‐Phe‐Pen‐NH2

… Journal of Peptide …, 1994

RGD peptides are known as important ligands for integrin receptors in the cell adhesion process. ... more RGD peptides are known as important ligands for integrin receptors in the cell adhesion process. The selectivity of RGD peptides for a certain integrin receptor is partly dependent on the RGD conformation and the residues surrounding the RGD sequence. This paper investigates the effect of the addition of a phenylalanine residue on the RGD conformation in cyclo(1,6)Ac-Cys-Arg-Gly-Asp-Phe-Pen-NH2 (1) as compared to the previously studied cyclo(1,5)Ac-Pen-Arg-Gly-Asp-Cys-NH2 (2). The conformational study of peptide 1 was done in aqueous solution using nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics simulations. This work will increase the understanding of the flanking residue's effect in RGD peptides.

Research paper thumbnail of Control of poorly soluble drug dissolution in conditions simulating the gastrointestinal tract flow. 2. Cocompression of drugs with buffers

Journal of pharmaceutical …, 1997

The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the prop... more The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the properties and flow dynamics of the liquid medium surrounding the tablet, as well as by the chemical nature of the drug. In this study, naproxen was used as a poorly soluble model drug. The dissolution medium was buffered with acetate, citrate, or phosphate buffer of varied concentrations and pH. GI flow conditions around a stationary tablet were simulated in a laminar flow device by anchoring the tablet on the floor of its channel having a rectangular cross section. Fresh, buffered solution was passed across the tablet and the effluent was collected for analysis and calculation of the dissolution rate. The dissolution rate was found to vary nonlinearly with the exposed tablet height, reaching a maximum at a tablet height approximately half the channel height. This maximum rate was attributed to an optimal combination of (1) eddy mixing and local turbulence generated by the flow impingement on the bluff object (tablet) and (2) the exposed tablet surface area available for dissolution. This effect was further confirmed by using dye-enhanced visual analysis of flow patterns at varied flow rates and exposed tablet heights. Elevation of the tablet to approximately the channel half-height significantly magnified the dissolution rate increase observed on exposure to buffered medium. Thus, tablet height and exposed surface area are major factors in determining dissolution rate, especially in conditions where the dissolving species reacts with the solvent. These results suggest that standard in vitro dissolution rate methods do not qualitatively indicate incremental changes in rate with altered tablet geometry or dissolution medium.