Effect Of Denaturation Research Articles

Effects of feed composition, protein denaturation and storage of milk serum protein/lactose powders on lactosylation

SummaryDuring whey powder production, the feed is subjected to several heat treatments which can cause lactosylation of proteins. In this study, lactosylation of whey proteins was evaluated in spray‐dried powders before and after storage by varying the native protein fraction as well as the serum protein/lactose ratio in the powders. The lactosylation of native α‐lactalbumin and β‐lactoglobulin in the powders before storage was not affected to a large extent by the protein denaturation or if the feed had been heat treated in a high or low lactose environment. After storage (relative humidity of 23.5%, 30 °C, 25 days), the kinetic of lactosylation tended to increase with increasing native protein fraction and bulk protein content in the powders. An explanation could be that proteins dissolved in the lactose glassy structure might have a lower reactivity, while proteins present in the protein glassy structure with dissolved lactose may display higher lactosylation reactivity.

Rheological Characterization of a Wood Adhesive Based on a Hydrolyzed Soy Protein Suspension

Soy protein (SP) is a promising raw material for the development of renewable and environmentally friendly adhesives. This work aims to study the effect of protein denaturation and/or hydrolysis on the rheology of a soy protein isolate (SPI) suspension. Four stages of chemical modification of SPI were evaluated: unmodified (U), denatured (D), partially hydrolyzed (PH) and fully hydrolyzed (H). Fourier-transform infrared spectroscopy (FTIR) and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) confirmed that polypeptides with high molecular weight were fully fragmented into smaller ones. Rheological analysis showed that U behaves as a gel-like material while PH and H act as viscous-like materials. Hydrolysis caused a significant decrease in the viscosity, even for suspensions with high solid content. Furthermore, comparing U and H, the viscosity at high shear strength dropped 65% with an increase of 219% in the solid content. The shear strength of the adhesives can be increased through two strategies: crosslinking with epoxy resin and the addition of different reinforcements. Considering suspension H as reference, the addition of 20% epoxy resin and 5% montmorillonite clay caused an increase in the shear strength of almost 39%. These results could contribute to the development of high solid content SP-based adhesive with desirable rheological properties and zero formaldehyde emission.

Denaturant-Mediated Modulation of the Formation and Drug Encapsulation Responses of Gold Nanoparticles.

The extensive and diversified applications of the well-known plasmonic nanoparticle systems along with their easy and environment-friendly synthesis strategies drive us to investigate in-depth this important research field. In the current scenario, our present study deals with an important plasmonic nanomaterial, i.e., globular protein, and human serum albumin (HSA)-conjugated gold nanoparticle (HSA-Au NP) system. The well-known chemical denaturants, urea and guanidine hydrochloride (GdnHCl or GnHCl), are investigated to show detrimental effects toward the formation of gold nanoparticles; however, the effect of GdnHCl is observed to be much prominent compared to that of urea. The synthesized nanoparticle system is found to be highly biocompatible from the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)-based cytotoxicity assay, and therefore, the applications of encapsulation of the well-known anticancer drug molecule, doxorubicin hydrochloride (Dox), in the nanoparticle system are further studied. In this drug encapsulation study, drug-metal complexation between Dox and HAuCl4·3H2O has been discussed elaborately. Similar to the nanoparticle formation, the effects of denaturants on drug encapsulation have also been discovered, and interestingly, it has been observed that urea plays a positive role, whereas GdnHCl plays a negative or detrimental role toward drug encapsulation in the synthesized gold nanoparticle system. The detailed photophysical mechanisms behind the drug encapsulation in the synthesized plasmonic nanosystem at every stage have also been explored. Overall, this study will conclusively explain the influences of the extensively used chemical denaturants on the synthesis and drug encapsulation behaviors of a well-known protein-conjugated gold nanoparticle, and as a consequence, it can be highly useful and acceptable to the biomedical and pharmaceutical research communities.

Co-delivery of terbinafine hydrochloride and urea with an in situ film-forming system for nail targeting treatment

Onychomycosis is a chronic nail disorder consisting of a fungal infection that causes physical and psychosocial discomfort to patients. However, its treatment remains challenging owing to the barrier of the highly keratinized nail plate and the short time that conventional formulations reside on nails. In this work, we developed an in situ film-forming system(IFFS) based on Eudragit® RLPO to co-deliver terbinafine hydrochloride (TBH) and urea, i.e., TBH-urea-RLPO IFFS, with the aim of overcoming the nail barrier, prolonging the residence time, and efficiently treating onychomycosis. The IFFS formulation formed a thin film with good appearance and adhesion upon application in situ. The physical states of TBH and urea in the film were evaluated with polarization microscopy and powder X-ray diffraction. TBH and urea were both amorphousmiscible components within the RLPO film. TBH release from TBH-urea-RLPO IFFS fitted to the Korsmeyer-Pappas model, and the cumulative release at 72h was significantly higher than that from commercial preparations (Lamisil Pedisan® once). In vitro permeation of TBH from TBH-urea-RLPO IFFS through bovine hoof membranes was evaluated in comparison with the film containing TBH alone (TBH-RLPO) and commercial preparations. The retention and cumulative permeated amount of TBH were significantly enhanced for the TBH-urea-RLPO IFFS (170.80±44.63μg/cm2vs 75.49±21.50μg/cm2vs 60.25±27.38μg/cm2; 61.81±16.09μg/cm2vs 21.80±11.56μg/cm2vs 7.91±1.03μg/cm2, respectively), and the membranes treated with different formulations were observed with SEM and FTIR to identify the denaturing effect of urea on bovine hoof keratin. In vitro antifungal tests against Trichophyton rubrum,Microsporum canis, Fusarium, and Aspergillus fumigatus were cultured on Muller-Hinton agar; the findings indicated that TBH-urea-RLPO IFFS enhanced TBH antifungal activity. Overall, the results support that TBH-urea-RLPO IFFS is an efficient and promising approach for onychomycosis targeting treatment.

Effects of feed composition, protein denaturation and storage of milk serum protein/lactose powders on rehydration properties

Whey powder rehydration is expected to be closely linked to both denaturation and lactosylation of the proteins. This study investigated the relation between the forced imbibition rate of spray-dried milk serum protein/lactose powders and the particle morphology and how it is related to the insoluble and lactosylated protein fraction, respectively. Despite extensive variation in protein denaturation, aggregation and lactosylation, only comparably small effects on the forced imbibition rate of the powders and the particle morphology could be observed. A possible explanation for this rather limited effect on the rehydration properties and particle morphology might be that the surface composition of the powder particles is rather similar and dominated by native proteins. These insights have relevance for the formulation of whey powders with improved rehydration properties.

Effects of the thermal denaturation of Sabin-derived inactivated polio vaccines on the D-antigenicity and the immunogenicity in rats

The efficacy of a Sabin-derived inactivated polio vaccine (sIPV) can be evaluated by measuring the immunogenicity and the contents of D-antigens, which induce the neutralizing antibodies. The immunogenic potency test in rats was done as a national assay in Japan. The two manufacturers of sIPV in Japan have performed both assays since development, and there is no clear discrepancy between the results obtained in the two assays. To further know the relationship between the two assays, we analyzed the effects of the heat treatment of sIPV on the D-antigenicity and the immunogenicity. We observed that the marginal D-antigen that remained after the thermal treatment was capable of inducing relatively high neutralizing antibodies in rats. This indicates that the measurement of the D-antigen contents as part of the quality control of sIPV is more sensitive and appropriate to detect denatured vaccines.

Effect of the Drying Temperature on Color, Antioxidant Activity and In Vitro Digestibility of Green Pea (Pisum sativum L.) Flour

AbstractGreen peas (Pisum sativum, cv. Warindo) are dehydrated in a channel air flowing (15 m s−1) drier at 50, 60, and 70 °C. Dried peas are milled for obtaining flour, and some properties are assessed. Increasing drying temperatures produce a significant greenness reduction (quantified by chroma parameter a) and on the relative crystallinity (assessed by X‐ray diffraction analysis) from ≈23% at 50 °C to 19% at 70 °C. Contrarily, the in vitro digestibility of both starch and protein increased as drying temperature is higher. The rapidly digestible starch increases from 15.94% at 50 °C to 36.48% at 70 °C, the effect that is linked to the reduction of the relative crystallinity, while protein digestibility increases from 76.26% at 50 °C to 85.87% at 70 °C. The increase of protein digestibility is ascribed to denaturation effects as detected by reduced content of β‐sheet secondary structures detected by FTIR analysis. From the consumer point of view, a higher protein digestibility is deemed as desirable, but the opposite holds true regarding starch digestibility. Thus, this work provides insights about the effect of drying temperature on the digestibility of starch and protein of green pea flour.

Effect of preheating-induced denaturation during protein production on the structure and gelling properties of soybean proteins

To explore the effect of preheating-induced denaturation during protein production on the structure and gelling properties of soybean protein isolates (SPI), protein neutralization solutions were preheated at various temperature for various periods and then spray-dried. The pre-denaturation degree (PDD) of SPI was quantitatively characterized by the change in the AB subunit using non-reducing SDS-PAGE. The onset denaturation time was 180 s, 40 s, and 10 s at preheating temperatures of 80 °C, 90 °C and 100 °C. As PDD increased, the contents of free sulfhydryl group and the ordered secondary structure gradually decreased, accompanied by the unfolding of the tertiary structure. Gel hardness, G′ and G″ increased at high PDDs, where the heating time required for gel formation decreased. The highly pre-denatured proteins (e.g., SPI86.11%, and SPI100%) formed gel network structures without heating. SEM images showed that the partially pre-denatured gels (SPI22.28% and SPI86.11%) were denser and had more uniform gel networks than the native protein (SPI0) and the completely pre-denatured protein (SPI100%). This work will provide guidelines for the control of heating conditions during SPI production process to improve gelling properties.

Pus solvents as new drugs with unique physical and chemical properti

The literature review shows that standards for the treatment of purulent diseases to date include antiseptic and disinfectants, but do not include agents that dilute and/or dissolve thick pus. It is shown that the pharmacodynamics of antiseptic and disinfectants consists in the local disinfecting effect of these agents. With local interaction with the surface of living and non-living tissues, these agents are able to sterilize it. It was found that for disinfection of the selected surfaces, these agents are used in solutions that contain these agents in concentrations that provide a denaturing effect. It is shown that denaturing action of antiseptic and disinfectants is a special case of dependence of local action of solutions of all medicines and chemical compounds on their concentration. The fact is that increasing the concentration of chemical compounds in solutions sooner or later turns that solutions into a liquid medium that is not compatible with life. Therefore, this liquid kills all cells of the micro-and macroworld. That is why the use of solutions with denaturing action provides a detrimental effect on the cells of all microorganisms and cells of the macroorganism. With local interaction with the tissues of the macroorganism, the drugs cause the following pharmacological effects: local sterilizing, irritating (local inflammatory) and cauterizing (necrotic) action. Thus solutions with denaturing concentration of one means increase the hardness, other means do not change the hardness, and the third means decrease the hardness of biological tissues, including purulent masses. From this it is concluded that today in the treatment of purulent diseases are used means, detrimental effect on all forms of life, and not means, unidirectionally acting on purulent masses. At the same time, it is shown that some of the modern antiseptic and disinfectants can change the properties of purulent masses in the right direction and optimize their removal by diluting and dissolving the thick pus. It is established that the leaders in the solvent action on thick and sticky pus are sodium bicarbonate solutions in combination with hydrogen peroxide. It is shown that solutions that effectively dissolve thick pus have special physical and chemical properties: all of them have moderate alkaline, temperature, boiling and osmotic activity. Preparations that most effectively dissolve thick pus and most quickly and completely remove it out of the purulent cavities, additionally contain carbon dioxide gas or oxygen gas under excessive pressure. In chronological order are recipes invented hygiene products with special physical and chemical properties, providing them with the ability to quickly and effectively liquefy, dissolve and remove the thick pus out of the purulent cavities. It is shown that a new group of hygiene products was discovered in Russia and was called Solvents of pus. The most effective and safe solvents of pus are warm (heated to a temperature of 42 C) solutions containing 24% sodium bicarbonate and 0.53% hydrogen peroxide.

Denaturant effect on amyloid fibrils: Declasterization, depolymerization, denaturation and reassembly

Accumulation of amyloid fibrils in organism accompanies many serious diseases, such as Alzheimer's and Parkinson's diseases, diabetes, prion diseases, etc. It is generally accepted that amyloids are highly resistant to degradation, which complicates their elimination in vivo and is one of the reasons for their pathogenicity. However, using a wide range of physicochemical approaches and specially elaborated method for the tested samples preparation by equilibrium microdialysis technique, it is proved that the stability of amyloids is greatly exaggerated. It turned out that amyloid fibrils formed from at least two amyloidogenic proteins, one of which is a model object for fibrils studying and the second is the cause of hemodialysis amyloidosis in an acute renal failure, are less stable than monomeric proteins. A mechanism of the degradation/reassembly of amyloid fibrils was proposed. It was shown that amyloid «seed» is a factor affecting not only the rate of the fibrils formation, but also their structure. Obtained results are a step towards identifying effects that can lead to degradation of amyloids and their clearance without adverse influence on the functionally active state of the protein or to change the structure and, as a result, the pathogenicity of these protein aggregates.

Phenolic profile and anti-inflammatory activity of four Moroccan date (Phoenix dactylifera L.) seed varieties

Date (Phoenix dactylifera L.) seeds are seen as good drug to cure rheumatoid arthritis and asthma in Moroccan traditional medicine. The present research aimed to study the anti-inflammatory effect, of methanol extract of different date seed varieties using membrane stabilizing effect, nitric oxide radical scavenging activity, inhibition of protein denaturation, carrageenan-induced paw edema and croton oil induced ear edema. The polyphenolic profile was examined using HPLC-DAD. Rutin, quercetin, p-coumaric and caffeic acids were the main among the analysed phenolic compounds. Concerning the anti-inflammatory activity, the analysed date seed were significantly effective in scavenging nitric oxide free radical, in stabilisation of erythrocyte membrane and possessed a high anti denaturation effect. In agreement with this finding, date seed exhibited a profound ability to reduce paw and ear swelling induced by carrageenan and croton oil respectively. The biochemical parameters showed that date seed are able to reduce the erythrocyte sedimentation rate (ERS) and C-reactive protein (CRP) concentration in rats used in Carrageenan-induced paw edema model. The predominant phenolic compounds are the potential candidates that drive these activities and the differences observed among varieties are related to their chemical composition. These data suggest that date seeds can be explored as a therapeutic agent for the treatment of inflammatory diseases.

GPCR Solubilization and Quality Control.

G protein-coupled receptors (GPCRs) are versatile membrane proteins involved in the regulation of many physiological processes and pathological conditions, making them interesting pharmacological targets. In order to study their structure and function, GPCRs are traditionally extracted from membranes using detergents. However, due to their hydrophobic nature, intrinsic instability in aqueous solutions, and theirdenaturing effects, theisolation of properly folded and functional GPCRs is not trivial. Therefore, it is of crucial importance to solubilize receptors under mild conditions and control the sample quality subsequently. Here we describe widely used methods for small-scale GPCR solubilization, followed by quality control based on fluorescence size-exclusion chromatography, SDS-PAGE, temperature-induced protein unfolding (CPM dye binding) and fluorescent ligand binding assay. These methods can easily be used to assess the thermostability and functionality of a GPCR sample exposed to different conditions, such as theuse of various detergents, addition of lipids and ligands, making them valuable for obtaining an optimal sample qualityfor structural and functional studies.

Matrix-assisted nanoelectrospray mass spectrometry for soft ionization of metal(i)–protein complexes

Metal ions play significant roles in biological processes, and investigation of metal-protein interactions provides a basis to understand the functions of metal ions in such systems. In the current study, a novel matrix-assisted nanoelectrospray ionization mass spectrometry (MANESI-MS) method was developed for investigating the interactions between metal ions (i.e., Cu+) and protein molecules (i.e., myoglobin) using Cu nanoparticles as the matrix. The results demonstrated that the present method not only was an efficient strategy for the generation of various complexes with monovalent metal ions, such as Cu+, in which no redox transitions between Cu+ and Cu2+ were observed, but also allowed a softer ionization of the generated Cu+-myoglobin complexes compared to that of myoglobin molecules with conventional nanoESI. Several parameters (i.e., the mixing mode of the myoglobin sample and Cu nanoparticle solution, size of the Cu particle, oxidation state of the Cu species, and acidity of the myoglobin solution) were found to be crucial in determining the ionization efficiency of the MANESI method. First loading a Cu nanoparticle solution into the electrospray tip followed by a myoglobin solution resulted in a favorable interaction between the generated Cu+ ions and myoglobin molecules, in which a smaller size of the Cu particle and a lower oxidation state of the metal species (Cu > Cu2O > CuO) gave a lower average charge state and hence a softer ionization of the resulting Cu+-myoglobin complexes, possibly due to the reduced denaturing effects of the Cu+ complex. The MANESI method has also been successfully used to ionize the complexes between Cu+ and other biological molecules such as cytochrome c and angiotension II, although an exception was found for lysozymes, which show an increase in the charge state. Analogous to the study with Cu, a variety of other metal nanoparticles (Ni, Fe, W, Ag, Al, Zn and Co) were explored to study their interactions with myoglobin, but only Zn and Co could produce monovalent metal ions (i.e., Zn+ and Co+) followed by a favorable interaction with myoglobin, and a soft ionization of the resulting complexes.

Could sodium lauryl sulfate be an irritant factor in oral mucosal desquamation?

Introduction: Oral mucosal desquamation (OMD) is an irritative reaction caused by products containing sodium lauryl sulfate (SLS), an anionic detergent that causes a stronger denaturation effect in intercellular structure epithelium. Case Series: Describing four cases of OMD induced by dentifrices, as an endeavor to make the condition better known, improving its diagnosis by clinicians based on minimal intervention. Conclusion: Oral mucosal desquamation should be considered as a differential diagnosis of the desquamative lesions of the mouth. Clinical signs and symptomatology should disappear in one week after discontinuation potentially involved products.

Protein packaging in ionic liquid mixtures: an ecofriendly approach towards the improved stability of β-lactoglobulin in cholinium-based mixed ionic liquids.

Ionic liquid (IL)-protein interaction studies are well documented; nonetheless, some families of ILs possess high toxicity which leads to the perturbation of biomolecules. However, ILs can be suitably designed by tweaking the constituent ions and also by amalgamating the mixture that stabilises the protein against the denaturing effect of another IL. To address this, the present study has explored the role of IL mixtures in imparting structural stability to protein β-lactoglobulin (β-LG). Previously, it was demonstrated that choline iodide ([Chn][I]) had an adverse effect on the native structure of β-LG. In order to counteract the deleterious action of [Chn][I], four IL mixtures (choline acetate [Chn][Ac] + [Chn][I] (MCACI); choline bitartrate [Chn][Bit] + [Chn][I] (MCBCI); choline chloride [Chn][Cl] + [Chn][I] (MCCCI); and choline dihydrogenphosphate [Chn][Dhp] + [Chn][I] (MCDCI)) were prepared in different ratios and their effects on the structural stability of β-LG were investigated. The UV-visible and fluorescence spectroscopy results revealed that β-LG achieved conformational changes with the addition of aqueous solutions containing mixtures of these ILs as compared to [Chn][I] alone. In near UV-CD spectroscopy, we observed that these four mixtures of ILs preserved the structure of β-LG by maintaining the tertiary structure. The dynamic light scattering (DLS) results demonstrated that the aqueous solutions containing IL mixtures decreased the dH values of β-LG, eventually keeping the compact structure of β-LG. These results confirm that the four biocompatible IL mixtures reduce the unavoidable aggregates of β-LG in the presence of [Chn][I]. Additionally, from the thermal fluorescence analysis, it was observed that the thermal stability of β-LG was enhanced by the four IL mixtures, thus counteracting the deleterious effect of [Chn][I] on β-LG. To the best of our knowledge, this work for the first time has demonstrated the role of choline-based IL mixtures in the structural transition of β-LG. The IL mixtures successfully enhanced the stability of the protein by reducing the perturbation caused by one of the components of the IL mixtures, thus amplifying the advantages of the other components. Overall, these results might find implications for understanding the role of IL mixtures towards protein folding/unfolding and pave a new direction for the development of eco-friendly protein-protective additives.

Urea Stress: Myo-inositol's efficacy to counteract destabilization of TIM-β-globin complex by urea is as good as that of the methylamine

Do kidney osmolytes counteract the deleterious effects of urea on kidney proteins? To answer this question, we measured guanidinium chloride (GdmCl)-induced denaturation of triose phosphate isomerase-β-globin subunit complex (TIM-β-globin) from sheep kidney in the presence of various concentrations of urea and each of kidney osmolytes (glycine betaine, myo-inositol and sorbitol) alone and in combination at pH 7.5 and 25 °C. Analysis of GdmCl-induced denaturation curve at a given osmolyte (or urea) concentration gave ΔGD0 (Gibbs free energy change in the absence of GdmCl). For a co-solute (CO), a linear plot of ΔΔGD0 (difference between values of ΔGD0 in the presence and absence of CO) against [CO] (molar concentration of CO) yielded m-value (=δΔΔGD0/δ[CO]). m-value for urea (murea) and that for the osmolyte (mosm) were used to determine [urea]:[osmolyte], the molar ratio for the perfect counteraction of the denaturing effect of urea on the protein stability by an osmolyte. For each osmolyte, we tested this ratio for the perfect counteraction. It was observed that glycine betaine and myo-inositol provide perfect counteraction at the predicted molar ratio whereas sorbitol fails to do so. Furthermore, urea and GdmCl induced a two-state denaturation, and both TIM and β-globin have identical thermodynamic stability.

Effects of Different Denaturants on Properties and Performance of Soy Protein-Based Adhesive.

Chemical modification of soy protein, via crosslinking, is the preferred method for creating non-toxic, renewable, environmentally friendly wood adhesives. The denaturing process of protein is important for the adhesive performance improvement. In order to investigate the effect of different denaturing agents on the performance of soy protein-based adhesives before and after crosslinking modification. In this study, three different denaturing agents—urea (U), sodium dodecyl sulfate (SDS), and sodium hydrogen sulfite (SHS) and an epoxide crosslinking agent—Triglycidylamine (CA) were used to prepare soy protein-based adhesives. The results showed: (1) The denaturing agent unfolded protein molecules and exposed more hydrophobic groups to prevent water intrusion, which was mainly a contribution for the water resistance and performance improvement of soy protein-based adhesives. The wet shear strength was improved up to 91.3% (denaturing by urea). (2) After modifying by the crosslinking agent, the properties and performance improvement was due to the fact that the active groups on soybean protein molecules reacted with the crosslinking agent to form a crosslinking structure, and there is no obvious correlation with the hydrophobic groups of the protein. (3) The unfolded soybean protein molecules also expose hydrophilic groups, which facilitates the reaction between the crosslinking agent and protein to form a denser crosslinking structure to improve the performance of the adhesive. Particularly, after denaturing with SHS, the wet shear strength of the plywood bonded by the SPI-SHS-CA adhesive increased by 217.24%.

Effect of Protein Denaturation and Enzyme Inhibitors on Proteasomal-Mediated Production of Peptides in Human Embryonic Kidney Cells.

Peptides produced by the proteasome have been proposed to function as signaling molecules that regulate a number of biological processes. In the current study, we used quantitative peptidomics to test whether conditions that affect protein stability, synthesis, or turnover cause changes in the levels of peptides in Human Embryonic Kidney 293T (HEK293T) cells. Mild heat shock (42 °C for 1 h) or treatment with the deubiquitinase inhibitor b-AP15 led to higher levels of ubiquitinated proteins but did not significantly increase the levels of intracellular peptides. Treatment with cycloheximide, an inhibitor of protein translation, did not substantially alter the levels of intracellular peptides identified herein. Cells treated with a combination of epoxomicin and bortezomib showed large increases in the levels of most peptides, relative to the levels in cells treated with either compound alone. Taken together with previous studies, these results support a mechanism in which the proteasome cleaves proteins into peptides that are readily detected in our assays (i.e., 6–37 amino acids) and then further degrades many of these peptides into smaller fragments.

Postprandial Amino Acid Kinetics of Milk Protein Mixtures are Affected by Composition, But Not Denaturation, in Neonatal Piglets

Multiple studies have indicated that formula-fed infants show a different growth trajectory compared with breastfed infants. The observed growth rates are suggested to be linked to higher postprandial levels of branched chain amino acids (BCAAs) and insulin related to differences in protein quality. We evaluated the effects of milk protein denaturation and milk protein composition on postprandial plasma and hormone concentrations. Neonatal piglets were bolus-fed randomly, in an incomplete crossover design, 2 of 3 milk protein solutions: native whey protein isolate (NWPI), denatured whey protein isolate (DWPI), or protein base ingredient, comprising whey and casein (PBI). Postprandial plasma amino acids (AAs), insulin, glucagon-like peptide 1, glucose, and paracetamol concentrations were assayed. Plasma responses were fitted with a model of first-order absorption with linear elimination. DWPI (91% denatured protein) compared with NWPI (91% native protein) showed lower essential amino acids (EAAs) (∼10%) and BCAA (13-19%) concentrations in the first 30-60 min. However, total amino acid (TAA) concentration per time-point and area under the curve (AUC), as well as EAA and BCAA AUC were not different. PBI induced a ∼30% lower postprandial insulin spike than NWPI, yet plasma TAA concentration at several time-points and AUC was higher in PBI than in NWPI. The TAA rate constant for absorption (k a) was twofold higher in PBI than in NWPI. Plasma BCAA levels from 60 to 180 min and AUC were higher in PBI than in NWPI. Plasma EAA concentrations and AUCs in PBI and NWPI were not different. Denaturation of WPI had a minimal effect on postprandial plasma AA concentration. The differences between PBI and NWPI were partly explained by the difference in AA composition, but more likely differences in protein digestion and absorption kinetics. We conclude that modifying protein composition, but not denaturation, of milk protein solutions impacts the postprandial amino acid availability in neonatal piglets.

A PROMISING DNA GROOVE BINDER AND PHOTOCLEAVER BASED ON A DINUCLEAR RUTHENIUM(II) COMPLEX

A dinuclear ruthenium complex [Ru2(bpy)4(bip-phenol)](ClO4)4 {bpy = 2,2′-bipyridine, bip-phenol = 2,4-bis(1 H -imidazo[4,5- f ][1,10]phenanthrolin-2-yl) phenol} has been synthesized and characterized. The calf thymus (ct) DNA binding properties of the complex are investigated by means of DNA viscosity and optical spectroscopic techniques of UV-visible absorption and emission spectral titrations, steady-state emission quenching with ferrocyanide, ethidium bromide competitive binding, DNA thermal denaturation and reverse salt effect, together with molecular simulation technology. The results suggest that the complex is a promising DNA groove binder with a large DNA binding constant on 106 M−1 order of magnitude. The fluorescence of the complex manifests by 6.3-fold upon binding saturately to DNA. The complex is also demonstrated to be an efficient photocleaver of pBR 322 DNA.