Biomedical subjects

Shan-Yang Lin

Publications and source records attributed to Shan-Yang Lin.

35 records · Page 2Linked to original sources

PubMed2004

Chronotherapeutic approach to design a thermoresponsive membrane for transdermal drug delivery.

In this review, the concepts of chronobiology, circadian rhythm, chronopharmacology, homeostasis and chronotherapy are taken into account to approach the optimal drug therapy, in which the timing of drug administration plays an important role. Based on these considerations, our laboratory has developed a thermo-responsive membrane by entrapping a single or binary liquid crystal to achieve an on-off switching drug delivery for transdermal application via the externally repeated cycle of temperature change, which may simulate the dosing time of therapeutic needs for human body.

Administration, Cutaneous↗

PubMed2003

Chondrogenesis of human mesenchymal stem cells encapsulated in alginate beads.

Mesenchymal stem cells (MSCs) have the capacity for self-renewal and can form bone, fat, and cartilage. Alginate forms a viscous solution when dissolved in 0.9% saline and gels on contact with divalent cations. The viability and phenotype maintenance of chondrocytes in alginate beads have been well documented. However, little is known about the effect of microencapsulation in alginate on chondrogenesis of MSCs. In this study, human MSCs encapsulated in alginate beads were cultured in serum-free medium with the addition of transforming growth factor (TGF)beta1 (10 ng/mL), dexamethasone (10(-7) M), and ascorbate 2-phosphate (50 microg/mL). The MSCs in alginate assumed a rounded morphology with lacunae around them after 1 week in culture. Cell aggregates were observed at 2 weeks or longer in culture. Histological findings agreed with the clinical determination of hyaline cartilage, characterized by isolated cells with ground substance positive in Safranin-O staining and immunohistochemistry for collagen type II at the periphery of cells. Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed the expression of COL2A1 and COL10A1, marker of chondrocytes and hypertrophy chondrocytes, respectively. These results indicate MSCs in alginate can form cartilage and the MSCs-alginate system represents a relevant model for the study of the molecular mechanisms involved in the chondrogenesis and endochondral ossification.

Alginates↗

PubMed2003

Fourier transform IR attenuated total reflectance spectroscopy studies of cysteine-induced changes in secondary conformations of bovine serum albumin after UV-B irradiation.

Fourier transform IR spectroscopy equipped with attenuated total reflection was used to investigate the cysteine-induced alteration of the protein secondary structure of bovine serum albumin (BSA) in aqueous solution before and after UV-B irradiation. Several amino acids were also studied. The results indicate the unchanged IR spectra of BSA coincubated with amino acids, except cysteine, did not change after 72-h UV-B irradiation. There was no difference in the IR spectrum of the unirradiated BSA coincubated with cysteine. A shoulder at 1620 cm(-1) attributed to the intermolecular beta-sheet structure was observed for the IR spectrum of BSA coincubated with cysteine after 72-h UV-B irradiation. Moreover, the peak intensity at 1303 cm(-1) that is due the alpha-helix structure was reduced, but the peak intensity at 1247 cm(-1) corresponding to beta-sheet structures was increased. Longer UV-B exposure for a BSA solution coincubated with cysteine changed the BSA solution from clear to viscous to gel form in which a transparent gel and another white gel were simultaneously observed. A gradual IR spectral alteration was found for BSA coincubated with cysteine and subjected to increased UV-B irradiation. The longer UV-B irradiation yielded increased intensity at 1620 cm(-1). The second-derivative IR peaks at 1655, 1631, and 1548 cm(-1) were shifted to 1650, 1620, and 1544 cm(-1), respectively, by the increase of UV-B irradiation, suggesting a progressive transformation from an alpha-helix to an intermolecular beta-sheet structure for BSA coincubated with cysteine. This strongly implies that longer UV-B exposure time for the BSA solution in the presence of cysteine did alter the protein secondary structures of BSA more, thus inducing gel formation by protein aggregation.

Amino Acids↗

PubMed2003

Fourier transform infrared spectroscopy used to evidence the prevention of beta-sheet formation of amyloid beta(1-40) peptide by a short amyloid fragment.

Reflectance Fourier transform infrared (FT-IR) microspectroscopy was applied to study the prevention of beta-sheet formation of amyloid beta (Abeta)(1-40) peptide by co-incubation with a hexapeptide containing a KLVFF sequence (Abeta(15-20) fragment). Second-derivative spectral analysis was used to locate the position of the overlapping components of the amide I band of Abeta peptide and assigned them to different secondary components. The result indicates that each intact sample of Abeta(15-20) fragment or Abeta(1-40) peptide previously incubated in distilled water at 37 degrees C transformed their secondary structure from 1649 (1651) or 1653cm(-1) to 1624cm(-1), suggesting the transformation from alpha-helix and/or random coil structures to beta-sheet structure. By co-incubating both samples with different molar ratio in distilled water at 37 degrees C, the structural transformation was not found for Abeta(1-40) peptide after 24h-incubation. But the beta-sheet formation of Abeta(1-40) peptide after 48h-incubation was evidenced from the appearance of the IR peak at 1626cm(-1) by adding a little amount of Abeta(15-20) fragment. There was no beta-sheet formation of Abeta(1-40) peptide after addition with much amount of Abeta(15-20) fragment, however, suggesting the higher amount of Abeta(15-20) fragment used might inhibit the beta-sheet formation of Abeta(1-40) peptide. The more Abeta(15-20) fragment used made the more stable structure of Abeta(1-40) peptide and the less beta-sheet formation of Abeta(1-40) peptide. The study indicates that the reflectance FT-IR microspectroscopy can easily evidence the prevention of beta-sheet formation of Abeta(1-40) peptide by a short amyloid fragment.

Amyloid beta-Peptides↗

PubMed2003

In vitro simulation of solid-solid dehydration, rehydration, and solidification of trehalose dihydrate using thermal and vibrational spectroscopic techniques.

PURPOSE: The processes of dehydration, rehydration, and solidification of trehalose dihydrate were examined to simulate it in the drying and wetting states. METHODS: Techniques included differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared (FT-IR) microspectroscopy combined with thermal analysis. Trehalose dihydrate was pressed on one KBr pellet (IKBr method) or sealed within two KBr pellets (2KBr method) for FT-IR measurement. RESULTS: On the DSC thermogram, the shoulder between 60 degrees C and 80 degrees C represented a transitional change because no weight loss occurred in this area of the TGA curve. The endothermic peak at 100 degrees C represented dehydration of trehalose dihydrate to anhydrous trehalose; a 9.5% weight loss in the TGA curve occurred from 81 degrees C. The thermal-dependent FT-IR spectra for trehalose dihydrate prepared by the IKBr method changed markedly with temperature in the 1800-1500 cm(-1) region during dehydration. IR peak intensity at 1687 cm(-1) assigned to the bending vibrational mode of solid-like water declined with temperature and decreased sharply at 67 degrees C. Another IR peak at 1640 cm(-1) associated with the bending of liquid water increased at 67 degrees C but disappeared at 79 degrees C as a result of water evaporation. Both peaks for the sample prepared by the 2KBr method changed dramatically at 64 degrees C; peak intensity at 1640 cm(-1) remained constant above 64 degrees C. CONCLUSIONS: A new polymorphic transition of trehalose dihydrate was first evidenced at 64-67 degrees C from both DSC curves and thermal-related FT-IR spectra. This transitional temperature reflected the thermal-dependent transformation from solid-like water to liquid water in the trehalose dihydrate structure during dehydration. During rehydration, trehalose anhydrate was rehydrated to the dihydrate, and liquid water in the dihydrate structure was again transformed to solid-like water. The polymorphic transition within this temperature range seems to correlate with the bioprotective effect of trehalose dihydrate in preserving protein stability.

Bromides↗

PubMed2003

Secondary conformations and temperature effect on structural transformation of amyloid beta (1-28), (1-40) and (1-42) peptides.

Secondary structure of three amyloid b-peptides [A beta(1-28), A beta(1-40) and A beta(1-42)] in the solid state was respectively determined by Fourier transform infrared (FT-IR) microspectroscopy. Their thermal-dependent structural transformation were also investigated by FT-IR microspectroscopy equipped with a thermal analyzer. The present result demonstrates that the solid-state A beta(1-28), A beta(1-40) and A beta(1-42) peptides showed a significant IR spectral difference in the amide I and II bands. The secondary conformation of A beta(1-28) peptide was the combination of major beta-sheet and minor alpha-helix with little random coil structures, but A beta(1-40) peptide showed the co-existence of major beta-sheet and minor random coil with little alpha-helix structures. A beta(1-42) peptide mainly consisted of the predominant b-sheet structure. Although the intact A beta(1-28), A beta(1-40) or A beta(1-42) peptide exhibits a different secondary structure, a similar beta-conformation may form after thermal treatment. A thermal-dependent transition was found for solid A beta(1-28) and A beta(1-40) peptides near 40 degrees C and 45 degrees C, respectively. There was no transition temperature for solid A beta(1-42) peptide, however, due to only a very little level of alpha-helix and random coil structure containing in the solid A beta(1-42) peptide. The thermal denaturation plays an important role in the structural transformation from alpha-helix/random coil to beta-sheet.

Amyloid beta-Peptides↗

PubMed2002

Hydration-induced proton transfer in the solid state of norfloxacin.

Norfloxacin is a special compound. Its hydrate form seems to be more soluble in water than in the anhydrate form. To investigate the hydration behavior of norfloxacin, the moisture-sorption analysis of anhydrous norfloxacin in different humidities was determined by using differential scanning calorimetry and thermogravimetric analysis. The contents of free water and bound water in the moisture-equilibrated norfloxacin were estimated quantitatively by using a curve-fitting program. Fourier transform infrared microspectroscopy with or without thermal analyzer was used to examine the structural change and dehydration process of norfloxacin in different humidities. The result indicates that the water content sorbed to anhydrous norfloxacin changed lightly below 51% relative humidity (RH) but increased markedly beyond 51% RH. The content of free water in the moisture-equilibrated norfloxacin was nearly to zero below 55% RH, but increased dramatically in high humidity. The content of bound water also enhanced gradually with the external humidity and reached to a constant of one unit after > 75% RH. When norfloxacin anhydrate transformed to its hydrate, the infrared peak intensity at 1732 and 1253 cm(-1) assigned to the C=O and C-O groups of carboxylic acid decreased gradually with the increase of water content, but the infrared peak intensity at 1584 and 1339 cm(-1) corresponding to asymmetric and symmetric carboxylates increased. Furthermore, the peak at 2553 cm(-1) assigned to the NH(+)(2) also appeared clearly and shifted from 2558 cm(-1) in higher water content and humidity. The main functional groups of norfloxacin changed from COOH to COO(-) and NH to NH(+)(2), attributable to the proton transfer from COOH group to NH group. This suggests that the hydration can induce the interaction between norfloxacin molecules from hydrogen bonding to ionic bonding by a proton-transfer process in the solid state.

Anti-Infective Agents↗

PubMed2002

Influence of excipients, drugs, and osmotic agent in the inner core on the time-controlled disintegration of compression-coated ethylcellulose tablets.

The effect of excipient, drug, and osmotic agent loaded in the inner core tablet on the time-controlled disintegration of compression-coated tablet prepared by direct compression with micronized ethylcellulose was investigated. The excipients [spray-dried lactose, hydroxypropyl methyl cellulose, sodium starch glycolate, microcrystalline cellulose, different drugs (sodium diclofenac: model drug, salbutamol sulfate, and theophylline anhydrate) and osmotic agent (sodium chloride)] were used to formulate the composition of the inner core tablet. The result indicates that drug release from all the compression-coated tablets was characterized by a distinctive lag of time followed by a faster drug release, dependent on the types of excipient and drug, and osmotic agent used in the inner core tablet. Respectively, the lag of time was 8.5, 12.4, 14.6, or 15.8 h for spray-dried lactose, hydroxypropyl methyl cellulose, sodium starch glycolate, or microcrystalline cellulose-loaded inner core tablet, as compared with 16.4 h for an inner core made of sodium diclofenac alone. The direct-compressible excipients such as spray-dried lactose, sodium starch glycolate, and microcrystalline cellulose seemed not to illustrate a marked disintegration function to rapidly rapture the outer coating layer. The lag of time was only slightly shortened from 16.4 to 14.6 h, >24 to 17.8 h, or >24 to 21.3 h for sodium diclofenac, theophylline anhydrate, or salbutamol sulfate incorporated with sodium starch glycolate into the inner core tablet, respectively, suggesting that sodium starch glycolate did not perform its superdisintegration. Once an osmotic agent of sodium chloride was incorporated into the inner core tablet, the lag of time for the compression-coated tablet was markedly shortened to <1 h, as compared with 16.4 h for drug alone. The more the amount of sodium chloride added, the less the time of lag obtained. Osmotic pressure did have a key role in controlling the drug dissolution. The present result implies that osmotic function is more suitable than superdisintegration function in designing a compression-coated tablet with time-controlled disintegration.

Albuterol↗

PubMed2002

Manufacturing factors affecting the drug delivery function of thermo-responsive membrane prepared by adsorption of binary liquid crystals.

A binary mixture of cholesteric oleyl carbonate (COC) and cholesteryl nonanoate (CN) with a weight ratio of 36% and 64% was adsorbed onto the cellulose nitrate membrane to prepare a thermo-responsive membrane. The thermo-responsive function of these COC/CN-adsorbed membranes was evaluated by an in vitro penetration study via repeatedly exchanging the temperature cycle. The manufacturing factors for preparing these thermo-responsive membranes, such as the binary COC/CN concentration used, immersion temperature of binary COC/CN chloroform solution, immersion temperature and time period of distilled water, vacuum-drying or air-drying process, and vacuum drying temperature, have been explored. The results indicated that the immersion temperature at 23 degrees C for membrane in binary COC/CN chloroform solution with 10 min and in distilled water with 12 h was the optimal temperature for fabricating the on-off thermo-responsive membranes prepared either by 22% or 25% concentration of binary COC/CN mixture. A good thermo-responsive function was further evidenced for these COC/CN-adsorbed membranes via vacuum-drying at 65 degrees C for 1 h. A possible mechanism concerning the thermal-dependent molecular motion, orientation and/or alignment of binary COC/CN mixture entrapped into the membrane may play an important role for the thermo-responsive behavior.

Adsorption↗

PubMed2002

Intramolecular cyclization of diketopiperazine formation in solid-state enalapril maleate studied by thermal FT-IR microscopic system.

The pathway of diketopiperazine (DKP) formation of solid-state enalapril maleate has been studied by using a novel Fourier transform infrared microspectroscope equipped with a thermal analyzer (thermal FT-IR microscopic system). The thermogram of the conventional differential scanning calorimetry (DSC) method was also compared. The results show new evidence of IR peaks at 3250 cm(-1) (the broad O-H stretching mode of water), and at 1738 and 1672 cm(-1) (the carbonyl band of DKP), indicating DKP formation in enalapril maleate via intramolecular cyclization. Moreover, the disappearance of IR peaks from enalapril maleate at 3215 cm(-1) (the secondary amine), 1728 cm(-1) (the carbonyl group of carboxylic acid), and 1649 cm(-1) (the carbonyl stretching of tertiary amide) also confirmed the DKP formation. The thermal FT-IR microscopic system clearly evidenced that the DKP formation in enalapril maleate started from 129 degrees C, and reached a maximum at 137 degrees C. This result was also confirmed by the conventional DSC thermogram of the compressed mixture of KBr powder and enalapril maleate, in which an endothermic peak at 144 degrees C with an extrapolated onset temperature at 137 degrees C was observed. This strongly suggests that the thermal FT-IR microscopic system was able to qualitatively detect the formation of DKP derivatives in solid-state enalapril maleate via intramolecular cyclization.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2002

Pressure-induced transformation of alpha-helix to beta-sheet in the secondary structures of amyloid beta (1-40) peptide exacerbated by temperature.

The effect of pressure on the conformational structure of amyloid beta (1-40) peptide (A beta(1-40)), exacerbated with or without temperature, was determined by Fourier transform infrared (FT-IR) microspectroscopy. The result indicates the shift of the maximum peak of amide I band of intact solid A beta(1-40) from 1655 cm(-1) (alpha-helix) to 1647-1643 cm(-1) (random coil) with the increase of the mechanical pressure. A new peak at 1634 cm(-1) assigned to beta-antiparallel sheet structure was also evident. Furthermore, the peak at 1540 cm(- 1) also shifted to 1527 (1529) cm(-1) in amide II band. The former was assigned to the combination of alpha-helix and random coil structures, and the latter was due to beta-sheet structure. Changes in the composition of each component in the deconvoluted and curve-fitted amide I band of the compressed A beta(1-40) samples were obtained from 33% to 22% for alpha-helix/random coil structures and from 47% to 57% for beta-sheet structure with the increase of pressure, respectively. This demonstrates that pressure might induce the conformational transition from alpha-helix to random coil and to beta- sheet structure. The structural transformation of the compressed A beta(1-40) samples was synergistically influenced by the combined effects of pressure and temperature. The thermal-induced formation of beta-sheet structure was significantly dependent on the pressures applied. The smaller the pressure applied the faster the beta-sheet structure transformed. The thermal-dependent transition temperatures of solid A beta(1-40) prepared by different pressures were near 55-60 degrees C.

Amides↗

PubMed2002

Thermal-induced changes in the secondary conformation of superoxide dismutase containing different metal ions.

The thermal stability of three superoxide dismutases (SODs) with different metal ions (Mn, Cu/Zn, Fe) in the solid state was studied by a Fourier transform infrared (FT-IR) microspectroscopy combined with thermal analyzer. The IR spectra showed a maximum peak at 1652 cm(-1) for all the native SODs in the amide I band, suggesting a predominant random coil with less alpha-helix structures. By heating each sample, a shoulder at 1631 cm(-1) in the amide I band gradually appeared from 45 degrees C for Fe SOD and from 50 degrees C for Mn SOD but another shoulder at 1639 cm(-1) appeared from 50 degrees C for Cu/Zn SOD. The peak at 1631 cm(-1) is due to the intermolecular beta-sheet structure, but the peak at 1639 cm(-1) corresponds to the major intramolecular beta-sheet with less random coil structure. This reveals that in the first heating process the transformation from random coil/alpha-helix structure to beta-sheet structure initiated from around 45-50 degrees C. There was about 16-22% compositional change resulting from that transformation. However, both additional shoulders stood there and did not restore to their original spectra even with cooling to room temperature, suggesting the denaturation and irreversible properties of the solid SODs after heating. The thermal-dependent denaturation and irreversibility of Mn SOD, Cu/Zn SOD and Fe SOD were clearly evidenced by the increase in intramolecular and intermolecular beta-sheet structure.

Animals↗

PubMed2002

Transformation of metastable forms of acetaminophen studied by thermal Fourier transform infrared (FT-IR) microspectroscopy.

A novel Fourier transform infrared (FT-IR) microspectroscopy equipped with a micro hot stage (thermal FT-IR microscopic system) was used to quickly study the phase transformation of acetaminophen polymorphs by a one-step process. Acetaminophen was sealed in KBr disc on the first and second heating processes under this system. The results indicate that the contour IR profile of form I acetaminophen in the first heating process changed dramatically only near 165 degrees C, but in the re-heating process exhibited a considerable alteration in peak intensity, band width and position near the temperatures at 85, 118 and 153 degrees C. A glassy form of acetaminophen was obtained after rapidly cooling the melted acetaminophen from 200 to 25 degrees C. The glassy acetaminophen was recrystallized at 85 degrees C to transform to the form III of acetaminophen in the reheating process, and then transformed to its form II near 118 degrees C. The thermal FT-IR microscopic system is a simple, quick and timesaving tool for investigation of the thermo-dependent molecular structure of acetaminophen polymorphs in the processes of recrystallization and polymorphic transition.

Acetaminophen↗

PubMed2002

PH-dependent coordination of metal-lisinopril complex investigated by attenuated total reflection/Fourier transform infrared spectroscopy.

In order to simulate the in vivo binding behavior of angiotensin-converting enzyme (ACE) inhibitors to the zinc-containing active center of ACE, the in vitro interaction between lisinopril and zinc or nickel ions was investigated in aqueous solutions of different pH by using attenuated total reflection (ATR)/Fourier transform infrared (FT-IR) spectroscopy with second-derivative IR spectral analysis. The results indicated that the lisinopril dissociation process occurred in a stepwise fashion during increase in pH. The IR peaks at 1642 cm(-1) (carbonyl stretching of tertiary amide) and at 1582 cm(-1) (asymmetric COO- stretching) for lisinopril in solution at pH 3.5 shifted to 1606 and 1586 cm(-1) after addition of Ni2+ ions, respectively, but there was no marked changes in IR spectra of lisinopril after addition of Zn2+ ions. When the Zn2+ ions were added to lisinopril solution at pH 5.0, the peak at 1642 cm(-1) also shifted to 1604 cm(-1) and the peak at 1582 cm(-1) shifted to 1586 cm(-1), similar to the changes at pH 3.5 after adding Ni2+ ions. However, the peaks at 1582 and 1642 cm(-1) both shifted to 1599 cm(-1) after addition of Ni2+ ions at pH 5.0 or at pH 7.3. The peak at 1576 cm(-1) also shifted to 1599 cm(-1) after addition of Zn2+ ions to lisinopril solution at pH 7.3. Different coordination sites or types (chelating, bridging or pseudounidentate complex) between lisinopril and Zn2+ or Ni2+ ions were proposed, based on the separation value between v(as) (COO-) and v(s) (COO-), and the shifting of carbonyl groups. Coordination of the secondary amine in lisinopril to metal ions was also evidenced.

Angiotensin-Converting Enzyme Inhibitors↗

PubMedDate not supplied

Ultrastructural and biophysical studies on protein conformations of epithelium and stroma in benign prostatic hyperplasia before and after transurethral resection of the prostate.

The alterations in protein conformation of epithelium and stroma in human benign prostatic hyperplasia (BPH) undergoing prostatic needle biopsy (PNB) and transurethral resection of the prostate (TURP) were isolated in vitro and investigated using attenuated total reflectance (ATR)/Fourier transform infrared (FT-IR) microspectroscopy. Second-derivative spectral analysis and a curve-fitting program were used to verify and obtain the protein secondary conformation and composition of the samples. TURP uses an electric cutting heat but PNB is a nonheating process. The results indicate a predominantly higher proportion of beta-sheet conformation of the epithelium or stroma in BPH tissue at 1633 or 1630 cm(-1) in the amide I band, but after treatment with TURP, both maximum peaks shifted to 1644 or 1646 cm(-1) due to random coil structure, respectively. This conversion suggests that the heat generated by the cutting loop could increase the temperature in the tissue surrounding the prostate, thereby modifying the protein conformational structure of epithelium and stroma in BPH tissue.

Aged↗

PubMedDate not supplied

Infrared microspectroscopic detection of epithelial and stromal growth in the human benign prostatic hyperplasia.

Benign prostatic hyperplasia (BPH) is one of the most common diseases in elderly men. It describes an overgrowth of the epithelial and fibromuscular tissues in the human prostate, in which both epithelium and stroma continue to proliferate at different rates. There is lack of suitable techniques for direct evaluation of the biophysical structure of molecular constituents and the proliferative changes in the structure of both compartments at the microscopic level. Reflectance Fourier transform infrared (FT-IR) microspectroscopy was used to pathologically image and examine the structural changes in the proliferation of epithelial and stromal tissues of human BPH. Two successive thin tissue slices were obtained by cutting the tissue with a microtome: one unstained slice was used for FT-IR spectroscopic analysis and the other stained slice was used for position referencing. The result indicates that the amide I maximum for BPH epithelial tissue was near 1,638 cm(-1) and showed its protein secondary structure by a combination of unordered and beta-sheet structures. However, an intense absorption band of amide I was at 1,630 cm(-1) for stromal BPH tissue due to the predominant beta-sheet structure. The higher peak intensity of several IR bands at 1,337, 1,281, 1,238, 1,206, 1,055, and 1,034 cm(-1), assigned to the C-O stretching mode of collagen, was observed in BPH stromal tissue. This suggests that the obvious collagen will be more enriched in the stroma of BPH tissue.

Aged↗

PubMedDate not supplied

Vibrational spectroscopic studies on the disulfide formation and secondary conformational changes of captopril-HSA mixture after UV-B irradiation.

The effects of pH and ultraviolet-B (UV-B) irradiation on the secondary structure of human serum albumin (HSA) in the absence or presence of captopril were investigated by an attenuated total reflection (ATR)/Fourier transform infrared (FTIR) spectroscopy. The UV-B exposure affecting the stability of captopril before and after captopril-HSA interaction was also examined by using confocal Raman microspectroscopy. The results indicate that the transparent pale-yellow solution for captopril-HSA mixture in all pH buffer solutions, except pH 5.0 approximately 7.0, changed into a viscous form then a gel form with UV-B exposure time. The secondary structural transformation of HSA in the captopril-HSA mixture with or without UV-B irradiation was found to shift the maxima amide I peak in IR spectra from 1652 cm(-1) assigned to alpha-helix structure to 1622 cm(-1) because of a beta-sheet structure, which was more evident in pH 3.0, 8.0 or 9.0 buffer solutions. The Raman shift from 1653 cm(-1) (alpha-helix) to 1670 cm(-1) (beta-sheet) also confirmed this result. Captopril dissolved in distilled water with or without UV-B irradiation was determined to form a captopril disulfide observed from the Raman spectra of 512 cm(-1), which was exacerbated by UV-B irradiation. There was little disulfide formation in the captopril-HSA mixture even with long-term UV-B exposure, but captopril might interact with HSA to change the protein secondary structure of HSA whether there was UV-B irradiation or not. The pH of the buffer solution and captopril-HSA interaction may play more important roles in transforming the secondary structure of HSA from alpha-helix to beta-sheet in the corresponding captopril-HSA mixture than UV-B exposure. The present study also implies that HSA has the capability to protect the instability of captopril in the course of UV-B irradiation. In addition, a partial unfolding of HSA induced by pH or captopril-HSA interaction under UV-B exposure is proposed.

Captopril↗