Hydrophobic probe binding of beta-lactoglobulin in the native and molten globule state induced by high pressure as affected by pH,KIO(3) and N-ethylmaleimide

High hydrostatic pressure (HHP) at 500 MPa and 50 degrees C induces beta-LG into the molten globule state. Retinol, cis-parinaric acid (CPA), and 1-anilino-naphthalene-8-sulfonate (ANS) fluorescence from pH 2.5 to 10.5 in the presence of the native and molten globule states of beta-LG indicate that retinol binds to beta-LG in the calyx, CPA at the surface hydrophobic site, and ANS in multiple hydrophobic sites. HHP treatment results in a decrease of beta-LG affinity for retinol and CPA, suggesting conformational changes in the calyx and surface hydrophobic site of beta-LG during HHP treatment. beta-LG treated by HHP in the presence of N-ethylmaleimide (NEM) retains retinol affinity, suggesting that NEM protects the calyx conformation of beta-LG during HHP treatment. HHP treatment of beta-LG in the presence of KIO(3) exhibits a great decrease of CPA affinity compared to HHP-treated beta-LG in the absence of KIO(3), suggesting the formation of non-native disulfide bonding at the CPA binding site.     

Probing the binding of the flavonoid diosmetin to human serum albumin by multispectroscopic techniques

The binding mechanism of molecular interaction between diosmetin and human serum albumin (HSA) in a pH 7.4 phosphate buffer was studied using atomic force microscopy (AFM) and various spectroscopic techniques including fluorescence, resonance light scattering (RLS), UV-vis absorption, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopy. Fluorescence data revealed that the fluorescence quenching of HSA by diosmetin was a static quenching procedure. The binding constants and number of binding sites were evaluated at different temperatures. The RLS spectra and AFM images showed that the dimension of the individual HSA molecules were larger after interaction with diosmetin. The thermodynamic parameters, ΔH° and ΔS° were calculated to be -24.56 kJ mol(-1) and 14.67 J mol(-1) K(-1), respectively, suggesting that the binding of diosmtin to HSA was driven mainly by hydrophobic interactions and hydrogen bonds. The displacement studies and denaturation experiments in the presence of urea indicated site I as the main binding site for diosmetin on HSA. The binding distance between diosmetin and HSA was determined to be 3.54 nm based on the F?rster theory. Analysis of CD and FT-IR spectra demonstrated that HSA conformation was slightly altered in the presence of diosmetin.     

Investigation of binding behavior of alpha- and beta-ionones to beta-lactoglobulin at different pH values using a diffusion-based NOE pumping technique

Diffusion-based NMR techniques were employed to study effects of pH on beta-lactoglobulin (BLG) conformation and binding affinity to alpha- and beta-ionone. In the first part of the study, the influence of pH on the diffusion coefficient of BLG in D(2)O solution was investigated using a stimulated-echo NMR experiment. The diffusion coefficient of BLG decreased with increasing pH values. A significant decrease in the diffusion coefficient observed at pH 11 may be due to total unfolding (denaturation) of the protein, resulting in hydrophobically driven self-aggregation. A diffusion-based NOE pumping technique was then applied to determine the relative binding affinities between alpha- and beta-ionones and BLG at pH values varying from 3 to 11. An increase in signal intensities for beta-ionone with increasing molar concentration ratios between beta-ionone and BLG was observed at all pH ranges studied. The increased signal intensities reflect increased relative binding affinity. The greatest binding affinity occurred at pH 9 and the lowest at pH 11. alpha-Ionone showed binding evidence only at pH 9, and the binding was significantly weaker than that obtained for beta-ionone at the same pH. The high affinity observed for both aroma compounds at pH 9 may be due to a flexible conformation of BLG at this pH so that the flavor ligand accessibility increases. Conversely, alkaline denaturation occurring at pH 11 gives rise to relatively lower binding affinity compared to that observed at the other pH values.     

A (1)H-NMR study on the effect of high pressures on beta-lactoglobulin

1H NMR was used to study the effect of high pressure on changes in the structure of beta-lactoglobulin (beta-Lg), particularly the strongly bonded regions, the "core". beta-Lg was exposed to pressures ranging from 100 to 400 MPa at neutral pH. After depressurization and acidification to pH 2.0, (1)H NMR spectra were taken. Pressure-induced unfolding was studied by deuterium exchange. Refolding was also evaluated. Our results showed that the core was unaltered at 100 MPa but increased its conformational flexibility at >/=200 MPa. Even though the core was highly flexible at 400 MPa, its structure was found to be identical to the native structure after equilibration back to atmospheric pressure. It is suggested that pressure-induced aggregates are formed by beta-Lg molecules maintaining most of their structure, and the intermolecular -SS- bonds, formed by -SH/-SS- exchange reaction, are likely to involve C(66)-C(160) rather than C(106)-C(119). In addition, the beta-Lg variants A and B could be distinguished in a (1)H NMR spectrum from a solution made with the AB mixed variant, by the differences in chemical shifts of M(107) and C(106); structural implications are discussed. Under pressure, the core of beta-Lg A seemed to unfold faster than that of beta-LgB. The structural recovery of the core was full for both variants.     

Conformational study of red kidney bean (Phaseolus vulgaris L.) protein isolate (KPI) by tryptophan fluorescence and differential scanning calorimetry

Fluorescence and differential scanning calorimetry (DSC) were used to study changes in the conformation of red kidney bean (Phaseolus vulgaris L.) protein isolate (KPI) under various environmental conditions. The possible relationship between fluorescence data and DSC characteristics was also discussed. Tryptophan fluorescence and fluorescence quenching analyses indicated that the tryptophan residues in KPI, exhibiting multiple fluorophores with different accessibilities to acrylamide, are largely buried in the hydrophobic core of the protein matrix, with positively charged side chains close to at least some of the tryptophan residues. GdnHCl was more effective than urea and SDS in denaturing KPI. SDS and urea caused variable red shifts, 2-5 nm, in the emission λ(max), suggesting the conformational compactness of KPI. The result was further supported by DSC characteristics that a discernible endothermic peak was still detected up to 8 M urea or 30 mM SDS, also evidenced by the absence of any shift in emission maximum (λ(max)) at different pH conditions. Marked decreases in T(d) and enthalpy (ΔH) were observed at extreme alkaline and/or acidic pH, whereas the presence of NaCl resulted in higher T(d) and ΔH, along with greater cooperativity of the transition. Decreases in T(d) and ΔH were observed in the presence of protein perturbants, for example, SDS and urea, indicating partial denaturation and decrease in thermal stability. Dithiothreitol and N-ethylmaleimide have a slight effect on the thermal properties of KPI. Interestingly, a close linear relationship between the T(d) (or ΔH) and the λ(max) was observed for KPI in the presence of 0-6 M urea.     

Interaction of flavonoids with bovine serum albumin: a fluorescence quenching study

The interaction between four flavonoids (catechin, epicatechin, rutin, and quercetin) and bovine serum albumin (BSA) was investigated using tryptophan fluorescence quenching. Quenching constants were determined using the Stern-Volmer equation to provide a measure of the binding affinity between the flavonoids and BSA. The binding affinity was strongest for quercetin and ranked in the order quercetin > rutin > epicatechin = catechin. The pH in the range of 5-7.4 does not affect significantly (p < 0.05) the association of rutin, epicatechin, and catechin with BSA, but quercetin exhibited a stronger affinity at pH 7.4 than at lower pH (p < 0.05). Quercetin has a total quenching effect on BSA tryptophan fluorescence at a molar ratio of 10:1 and rutin at approximately 25:1. However, epicatechin and catechin did not fully quench tryptophan fluorescence over the concentration range studied. Furthermore, the data suggested that the association between flavonoids and BSA did not change molecular conformation of BSA and that hydrogen bonding, ionic, and hydrophobic interaction are equally important driving forces for protein-flavonoid association.     

Effect of heat treatment on bovine beta-lactoglobulin A, B, and C explored using thiol availability and fluorescence.

Dilute solutions of beta-lactoglobulin (beta-Lg) A, B, and C were heated at temperatures between about 40 and 94 degrees C for 10 min, cooled, and analyzed using Trp fluorescence and extrinsic fluorescence spectra of the probe 1,8-anilinonaphthalene sulfonate (ANS). Thiol availabilities using 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) were determined using a separate set of samples. The normalized ANS fluorescence emission intensity and the thiol availability results showed a 1:1 relationship with the loss of nativelike but not SDS-monomeric protein, as determined by PAGE analysis. The normalized Trp emission intensity results did not show a comparable 1:1 relationship with the loss of nativelike protein, indicating that the Trp intensity arose from consequential disulfide bond reorganization and not the initial unfolding reaction. The results were also analyzed in terms of two-state models, and the midpoint temperatures (T(mid)) for the proteins were generally beta-Lg C > beta-Lg A > beta-Lg B, and the slopes at the midpoint temperatures for the A variant were generally less than those for the B and C variants indicating that beta-Lg A may denature by a different mechanism from that of beta-Lg B or beta-Lg C. The T(mid) parameters derived from the ANS fluorescence intensity results were similar to those for thiol availability and both were lower than the T(mid) values for Trp emission intensity showing that creation of an ANS binding site on a beta-Lg molecule was linked to the irreversible exposure of a thiol group and the loss of native beta-Lg but preceded the decrease in Trp(61) fluorescence quenching. These results for the differences between the behavior of the A and B or the C variants involved the creation of a destabilizing cavity by the Val(118)Ala (A --> B) substitution and the changed charge distribution within the CD loop caused by the Asp(64)Gly (A --> B) substitution.     

Nuclear magnetic resonance spectroscopic study of beta-lactoglobulin interactions with two flavor compounds,gamma-decalactone and beta-ionone

Interactions between a well-characterized protein, beta-lactoglobulin, and two flavor compounds, beta-ionone and gamma-decalactone, were studied by 2D NMR spectroscopy. NMR spectra were recorded in aqueous solution (pH 2.0, 12 mM NaCl, 10% D(2)O) under conditions such that beta-lactoglobulin is present in a monomeric state. TOCSY and NOESY spectra were recorded on the protein and the complexes between protein and ligands. The spectra of the NH-CH(alpha) region showed the cross-signals due to the coupling between N- and C-bonded protons in the polypeptide backbone. The observed chemical shift variations in the presence of ligands can be assigned to changes in the protein conformation. It appears that the side chains of several amino acids are affected by binding of gamma-decalactone point into the central cavity (Leu46, Ile56, Met107, and Gln120), whereas binding of beta-ionone affects amino acids located in a groove near the outer surface of the protein (Leu104, Tyr120, and Asp129), as illustrated by molecular visualization. This NMR study provides precise information of the location of binding and confirms the existence of two different binding sites for aroma compounds on beta-lactoglobulin, which was suggested in previous competition studies by fluorometry or affinity chromatography and by structural information obtained from infrared spectroscopy.     

Conformational and rheological changes in catfish myosin as affected by different acids during acid-induced unfolding and refolding

Changes in the conformation of catfish (Ictalurus punctatus) myosin due to (i) anions, (ii) acid pH, and (iii) salt addition were determined using tryptophan fluorescence, hydrophobicity measurements, differential scanning calorimetry, and circular dichroism. The relationship between conformation and storage modulus (G') of acid-treated myosin was studied. Three acids, HCl, H2SO4, and H3PO4, were used for unfolding myosin at three acidic pH conditions, 1.5, 2.0, and 2.5. Unfolded myosin was refolded to pH 7.3. Denaturation and unfolding of myosin was significantly (p < 0.05) lower when salt (0.6 M NaCl) was present during acid unfolding than in the absence of salt. When salt was added before unfolding, the alpha-helix content of myosin treated at pH 1.5 was significantly lower than that treated at pH 2.5. When salt was added after refolding, the alpha-helix content of myosin was unaffected by different pH treatments. The G' of myosin increased with an increase in myosin denaturation. The G' of myosin was significantly (p < 0.05) higher when salt was added to myosin after refolding than before acid unfolding. Among the different anion treatments, the G' of acid-treated myosin decreased in the order Cl- approximately SO42- > PO43-. Among the different pH treatments, the G' of myosin treated at pH 1.5 was significantly (p < 0.05) higher than myosin treated at pH 2.5. The conditions that would result in maximum myosin denaturation and maximum G' were unfolding of myosin at pH 1.5 using Cl- (from HCl) followed by refolding at pH 7.3 and subsequent addition of 0.6 M NaCl.     

Comparison of protein surface hydrophobicity measured at various pH values using three different fluorescent probes

The influence of type of fluorescent probe on the surface hydrophobicity values determined for three native and heated proteins was assessed using uncharged [6-propionyl-2-(N, N-dimethylamino)naphthalene or PRODAN] versus anionic aliphatic (cis-parinaric acid or CPA) and aromatic (1-anilinonaphthalene-8-sulfonic acid or ANS) probes. Surface hydrophobicities of whey protein isolate, beta-lactoglobulin, and bovine serum albumin under heated (80 degrees C for 30 min) and unheated conditions and at varying pH values (3.0, 5.0, 7.0, and 9. 0) were measured using ANS, CPA, and PRODAN. ANS and CPA yielded opposing results for the effects of pH and heating on protein hydrophobicity. Hydrophobicity was lower at pH 3.0 than at other pH values for all proteins measured by PRODAN, whereas the values measured by ANS and CPA at pH 3.0 were quite high compared to those at other pH values, suggesting the influence of electrostatic interactions on anionic probe-protein binding. These results suggest that the presence or absence of a permanent charge as well as the aromatic and aliphatic nature of fluorescent probes can affect protein hydrophobicity values measured under various pH conditions.     

Beta-lactoglobulin molten globule induced by high pressure.

Beta-lactoglobulin (beta-LG) was treated with high hydrostatic pressure (HHP) at 600 MPa and 50 degrees C for selected times as long as 64 min. The intrinsic tryptophan fluorescence of beta-LG indicated that HHP treatment conditions induced a conformational change. HHP treatment conditions also promote a 3-fold increase in the extrinsic fluorescence of 1-anilinonaphthalene-8-sulfonate and a 2.6-fold decrease for cis-paraneric acid, suggesting an increase in accessible aromatic hydrophobicity and a decrease in aliphatic hydrophobicity. Far-ultraviolet circular dichroism (CD) spectra reveal that the secondary structure of beta-LG converts from native beta-sheets to non-native alpha-helices following HHP treatment, whereas near-ultraviolet CD spectra reveal that the native tertiary structure of beta-LG essentially disappears. Urea titrations reveal that native beta-LG unfolds cooperatively, but the pressure-treated molecule unfolds noncooperatively. The noncooperative state is stable for 3 months at 5 degrees C. The nonaccessible free thiol group of cysteine121 in native beta-LG became reactive to Ellman's reagent after adequate HHP treatment. Gel electrophoresis with and without beta-mercaptoethanol provided evidence that the exposed thiol group was lost concomitant with the formation of S-S-linked beta-LG dimers. Overall, these results suggest that HHP treatments induce beta-LG into hydrophobic molten globule structures that remain stable for at least 3 months.     

Influence of pH on Structure and Function of Amaranth (Amaranthus hypochondriacus) Protein Isolates

Structural and functional properties of two amaranth protein isolates as a function of pH were studied. Isolates, A9 and A11, were obtained by alkaline extraction at pH 9 and 11, respectively. Gel filtration chromatograms of A9 and A11 showed similar profiles. The A11 isolate contained mainly albumins and globulins, and a small proportion of globulin‐P aggregates, suggesting the presence of species with a higher degree of denaturation compared to A9. Differential scanning calorimetry (DSC) showed that A9 was characterized by two thermal transitions (65.8 and 98°C); A11 exhibited only a small endotherm (66.6°C) and a second, less defined one. DSC analysis of A9 at pH 2–4 did not show endotherms, but at pH 5, some protein structures were observed. A11 showed a greater degree of denaturation. FPLC results showed that the proteins in A9 are more folded and their conformation is closer to the native state than those in A11, which are more unfolded due to pH‐mediated denaturation, mainly in acid media. The surface hydrophobicity of the isolates in acid media was lower than in alkaline media. The fluorescence emission spectra of the isolates showed differences in acidic pH conditions. As expected, the highest solubility was at alkaline pH. The water‐holding capacity was similar for both isolates. The water‐imbibing capacity and speed of foaming was higher for A11 than for A9. In summary, intense pH treatment of amaranth isolates generated partial or total protein denaturation and differences in the functional properties.     

基于前表面荧光光谱鉴别新鲜与冻融大黄鱼

为研究反复冻融对水产品品质的影响,通过理化方法检测了不同冻融次数处理对大黄鱼解冻损失、pH 值、色泽、硫代巴比妥酸值、羰基含量等指标的影响,并采用前表面荧光光谱结合主成分分析（principal component analysis,PCA）和 Fisher 线性判别分析法（Fisher linear discriminant analysis,FLDA）对不同冻融次数的大黄鱼进行区分。结果显示随着冻融次数增加,大黄鱼的解冻损失显著增加（P<0.05）;pH 值呈先上升后下降的趋势;L*（亮度）值、b*（黄度）值均有不同程度的增加（P<0.05）,a*（红度）值下降（P<0.05）;羰基含量和硫代巴比妥酸反应物值（thiobarbituric acid reactive substances,TBARS）增加（P<0.05）,反复冻融导致大黄鱼的品质下降。色氨酸和烟酰胺腺嘌呤二核苷酸磷酸（nicotinamide adenine dinucleotide,NADH）的荧光光谱分别结合 PCA 和 FLDA 对不同冻融处理组进行分析,结果表明 FLDA 识别效果优于 PCA。通过 FLDA 建立了新鲜大黄鱼与冻融大黄鱼荧光光谱判别模型,发现色氨酸原始判别的准确率和交叉验证的准确率分别为68.3%和66.7%,NADH 原始判别的准确率和交叉验证的准确率均达到100%。由此可见,利用 NADH荧光光谱结合化学计量分析可以鉴别不同冻融处理的大黄鱼。研究结果为水产品新鲜度的快速评价提供参考。     

Bioevaluation of human serum albumin-hesperidin bioconjugate: insight into protein vector function and conformation

Hesperidin is a flavanone glycoside widely available for dietary intake in citrus fruits or citrus fruit derived products; however, exhaustive and reliable data are scarcely available for biological activity when it exerts protective health effects in humans. The principal intent of this work is to check binding domain and structural changes of human serum albumin (HSA), the primary carrier of flavonoids, in blood plasma association with hesperidin by employing molecular modeling, steady state and time-resolved fluorescence, and circular dichroism (CD) methods. From molecular modeling simulations, subdomains IIA and IIIA, which correspond to Sudlow's sites I and II, respectively, were earmarked to possess affinity for hesperidin, but the affinity of site I with flavanone is greater than that of site II. This corroborates the site-specific probe and hydrophobic 8-anilino-1-naphthalenesulfonic acid (ANS) displacement results placing the hesperidin at warfarin-azapropazone and indole-benzodiazepine sites. Steady state and time-resolved fluorescence manifested that static type, due to HSA-hesperidin complex formation (1.941 × 10(4) M(-1)), is the operative mechanism for the diminution in the tryptophan (Trp)-214 fluorescence. Moreover, via alterations in three-dimensional fluorescence and CD spectral properties, we can securely draw the conclusion that the polypeptide chain of HSA is partially destabilized after conjugation with hesperidin. We anticipate that this study can provide better knowledge of bioavailability such as absorption, biodistribution, and elimination, of hesperidin in vivo, to facilitate the comprehension of the biological responses to physiologically relevant flavanones.     

Tryptophan-N-glucoside in fruits and fruit juices

In extracts prepared from various fruits as well as in fruit juices a single tryptophan glycoconjugate was detected by HPLC-MS analysis. Product ion spectra demonstrated the N-glycosidic linkage of a hexose moiety to the indole nitrogen. For structure elucidation, the novel tryptophan glycoside was isolated from pear juice and identified as N(1)-(beta-D-glucopyranosyl-(4)C(1))-L-tryptophan by (1)H, HH-COSY and (13)C NMR spectroscopy. Finally, we disclosed the biosynthetic origin of the novel tryptophan metabolite by demonstrating the enzymatic glycosylation of deuterium-labeled tryptophan, which was applied to pear fruit.     

Stability to light, heat, and hydrogen peroxide at different pH values and DPPH radical scavenging activity of acylated anthocyanins from red radish extract

The stability of red radish extract to light, heat, and hydrogen peroxide at different pH values (3, 5, and 7) was examined, in which major anthocyanins were pelargonidin glycosides acylated with a combination of p-coumaric, ferulic, or caffeic acids. The light irradiation (fluorescence light, 5000 lx; at 25 degrees C) indicated that the red radish extract was more stable at lower pH than at higher pH. The HPLC analyses revealed that diacylated anthocyanins in the extract were more stable to light at pH 3 than monoacylated anthocyanins. No significant difference in degradation rates of acylated anthocyanins at pH 5 was observed, whereas anthocyanins acylated with p-coumaric or ferulic acids were more stable at pH 7 than ones with caffeic acids. The stability to heat (at 90-95 degrees C) showed a tendency similar to that for light. The number of intramolecular acyl units contributes to stability to light and heat at lower pH, whereas the characteristics of intramolecular acyl units influence the stability at higher pH. The degradation behavior of red radish extract to H2O2 were almost the same to those of light and heat, depending on the pH. However, HPLC analyses revealed that the stability of individual acylated anthocyanins were independent of the pH. These data suggest that the characteristics, the number, and the binding site of intramolecular acyl units affect the stability of anthocyanin to H2O2. DPPH radical scavenging activity of all acylated anthocyanins was higher than those of pelargonidin and perlargonidin-3-glucoside. The activity of acylated anthocyanins mostly depended on the activity of intramolecular acyl units (caffeic acid > ferulic acid > p-coumaric acid). However, the activity was highly affected by the binding site of intramolecular acyl units even if anthocyanins have common acyl units.     

Characterization of 2-methyl-4-amino-5-(2-methyl-3-furylthiomethyl)pyrimidine from thermal degradation of thiamin

Thiamin hydrochloride was thermally degraded in phosphate buffer (pH 6.5) at 110 degrees C for 2 h. A major decomposition product was isolated by column chromatography and structurally identified by spectrometric techniques ((1)H NMR, (13)C NMR, 2D NMR, and MS) as 2-methyl-4-amino-5-(2-methyl-3-furylthiomethyl)pyrimidine (MAMP). The possible formation pathway of MAMP was studied using two model systems. It is proposed that MAMP is formed by nucleophilic attack of 2-methyl-3-furanthiol on the thiamin.     

Effect of ultrahigh hydrostatic pressure on the activity and structure of mushroom (Agaricus bisporus) polyphenoloxidase

High hydrostatic pressure (HHP, treatment pressure ≤700 MPa) is approved to be the most successful commercial nonthermal processing due to its minimal modifications in nutritional and sensory quality. However, for some pressure stable enzymes such as PPO, this unique technology can hardly inactivate them at treatment pressure below of 700 MPa. This study investigated the effects of ultrahigh hydrostatic pressure (UHHP, treatment pressure >700 MPa) on the activity of Agaricus bisporus mushroom polyphenoloxidase (PPO) both in the phosphate buffer and in the mushroom puree, and on the structure of the enzyme by means of circular dichroism (CD), fluorescence emission spectra, and sulphydryl group detection. The results showed that UHHP treatment at pressure from 800 to 1600 MPa caused significant inactivation on the PPO both in the phosphate buffer and in the mushroom puree. UHHP treatment at 1400 and 1600 MPa for 1 min reduced the enzyme activity by 90.4% and 99.2% in the buffer;, however, higher enzyme activity remained in the puree after UHHP treatment at the same condition. CD and fluorescence spectra analysis showed that the secondary and tertiary structures of UHHP treated mushroom PPO were changed. The sulphydryl group (SH) detection revealed that the SH content on the surface of UHHP treated mushroom PPO was increased. It has been suggested that the inactivation of mushroom PPO by UHHP treatment at pressure higher than 1000 MPa was due to the synergistic effect of the pressure and the heat arising from pressurization, in which heat plays a major role.     

Phosphorylation of ovalbumin by dry-heating in the presence of pyrophosphate: effect on protein structure and some properties

Ovalbumin (OVA) was phosphorylated by dry-heating in the presence of pyrophosphate at pH 4.0 and 85 degrees C for 1 and 5 days, and the physicochemical and structural properties of phosphorylated OVA were investigated. The phosphorus content of OVA increased to 1.01% by phosphorylation, and the electrophoretic mobility of PP-OVA also increased. Although the solubility of dry-heated OVA decreased, the decrease was slightly depressed by phosphorylation. The circular dichroism spectra showed that the change of the secondary structure in the OVA molecule, as measured by alpha-helix content, was mild by phosphorylation. The exchange reaction between the sulfhydryl and disulfide groups was enhanced and the surface hydrophobicity of OVA increased by phosphorylation. The tryptophan fluorescence intensity of OVA decreased by phosphorylation, suggesting that the conformational change occurred in the OVA molecule by phosphorylation. Although the differential scanning calorimetry thermograms of OVA showed a lowering of the denaturation temperature from 78.3 to 70.1 degrees C by phosphorylation, the stability of OVA against heat-induced insolubility at pH 7.0 was improved. The results indicated molten (partially unfolded) conformations of OVA formed by dry-heating in the presence of pyrophosphate.     

Interaction between morin and sodium dodecyl sulfate (SDS) micelles

Electronic absorption spectra, fluorescence emission spectra, ATR-FTIR spectra, cyclic voltammetric measurements, and ab initio quantum calculation are used to study the properties of morin in SDS micelles of different microstructures and microenvironments and to gain the information about the binding of morin with the SDS micelles. Morin can be located in the SDS micelles with its phenyl group (deviating by 38.98 degrees from the planarity), which leads to the increase of the planarity and the extension of pi conjugation of the whole molecule. The embedment of two hydroxyl groups on the phenyl into a more hydrophobic microenvironment makes the oxidation peak of morin move to a higher potential with a decreased peak current. The binding constant (K) and the distribution coefficient (P) of morin in the spherical SDS micelle are larger than those in the rodlike SDS micelle. The binding of morin with SDS micelle is a spontaneous (DeltaG < 0) and exothermic process (DeltaH < 0), and the hydrophobic force is the main driving force for its solubilization.