Article pubs.acs.org/jced
Influence of Urea on Shifting Hydrophilic to Hydrophobic Interactions of Pr(NO3)3, Sm(NO3)3, and Gd(NO3)3 with BSA in Aqueous Citric Acid: A Volumetric, Viscometric, and Surface Tension Study Dinesh Kumar,† Abhishek Chandra,† and Man Singh*,† †
School of Chemical Science, Central University of Gujarat, Gandhinagar-382030, India S Supporting Information *
ABSTRACT: Density, surface tension, and viscosity for hexahydrate nitrate salts of praseodymium, samarium, and gadolinium from (0.023 to 0.150) mol·kg−1 in aqueous solutions of: (a) citric acid (1.11 mol·kg−1), (b) citric acid + urea, (c) citric acid + bovine serum albumin, and (d) citric acid + urea + bovine serum albumin at 298.15 K and atmospheric pressure are reported. By using densities and viscosities, the apparent molar volumes, limiting apparent molar volumes, apparent molar transfer volumes, and viscosity B-coefficients have been calculated. The varying trends of aforesaid physicochemical parameters have been interpreted in light of the solute−solvent and solute−solute interactions. An attempt has thus been made to investigate the influence of urea on the interacting activities of lanthanide nitrate with citric acid and the critical role being played by bovine serum albumin in decoding the dominance of hydrophilic−hydrophobic interactions. of BSA inducing conformational changes in BSA.17 Samarium exhibits intense and long-lived photoluminescence, which shows great promise for luminescent biodetection in vitro.12 In recent years, proteins and especially BSA have been used to modify the surface properties of the lanthanide nanoparticles (LNP) and thus has drawn a wider and deeper attention.18 Since for biological activity of LNP’s, their sizes19−22 and surface chemistry23−25 are of utmost importance; thus, it is of considerable interest to investigate the behavior of lanthanide ions (Ln3+) like Pr3+, Sm3+, and Gd3+ in a biological environment through the physicochemical study that could help to design better functionalized LNPs. There are several studies on interaction of proteins with surfactants, metal ions, and transition metal complexes,26−29 but there is a severe lack of study on the interaction of Ln3+ salts with BSA through physicochemical properties (PCP) because they denature and aggregate the protein in aqueous medium, hindering the study in aqueous medium. In view of this, the interaction study was carried out in 1.11 mol·kg−1 aqueous citric acid to stop the aggregation of BSA on Ln(NO3)3 addition. Additionally, the impact of urea (U) on these interactions has also been studied to distinguish the changing modes of interactions in its presence. Since urea is a powerful protein denaturant, the study was carried out with 0.1 mol·kg−1 urea concentration, which is below its concentration of denaturation [(6 to 8) mol·
1. INTRODUCTION It is well-known that proteins play the central role in supporting life and are closely related to the origin, advancement, and metabolism of life. Serum albumins are abundantly found in blood plasma and belong to one of the most widely studied categories. They have a wide range of physiological functions involving binding, transport, and function as carriers of metal ions, fatty acids, porphyrins, bilirubin, and steroids, etc. Furthermore, albumin plays an active role in drug admission and maintenance of blood pressure in the body.1−3 In view of its water-soluble nature and well-characterized structure, bovine serum albumin (BSA) has been often utilized as protein model system for the study of interactions.4 In recent years, lanthanides have attracted significant attention of the researchers owing to their outstanding optical, luminescence, and magnetic properties.5−11 These unique potential and enriched abilities enable them to be used extensively in screening and diagnostic applications pertaining to biological domain such as drug delivery, fluorescent probes, bioimaging, biosensors,12 and contrasting agents in MRI scans.13,14 Among these, gadolinium has been used to assist imaging of blood vessels and inflamed tissue, viewing intracranial lesions with abnormal vascularity and abnormalities in the blood−brain barrier. Its paramagnetic property reduces the T1 relaxation time and to some extent the T2 and T2* relaxation times in NMR and is the source of its clinical utility.15 Praseodymium has been used as near-infrared luminescent biolabels for the sensitive detection of biomolecules16 and is also known to quench the intrinsic fluorescence © 2014 American Chemical Society
Received: June 12, 2014 Accepted: October 23, 2014 Published: November 4, 2014 3643
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Table 1. Specifications of Chemicals Used
a
name
puritya
samarium(III) nitrate hexahydrate praseodymium(III) nitrate hexahydrate gadolinium(III) nitrate hexahydrate citric acid urea BSA
≥99.9% ≥99.9% ≥99.9% ≥99.5% ≥99% ≥98%
waterb (%) < < < < <
CO group of the U. BSA inclusion to WC resulted in the development of stronger hydrophilic−hydrophilic interaction (HHI) between BSA and C due to the higher interacting activities of NH3+, −COO−, and >CO of BSA and −COO− and −OH of C. This resulted in overlapping of BSA hydration sphere with the C hydration sphere, triggering an increase in volume due to release of water molecules from the hydration spheres to the bulk with ρ value of WCB < WC. Similarly, the addition of BSA to WCU causes the release of water molecules to the bulk, but the increase in volume is less due to the presence of stronger HHI between U and W with a ρ value of WCB < WCUB. From Tables 2 to 4, it is evident that, in general, on addition of 0.0252 mol·kg−1 of Pr(NO3)3 to WC, the density increases by 0.64 %, while with WCB it increases by 0.73 %. Interestingly, the addition of 0.0252 mol·kg−1of Pr(NO3)3 to WCU and WCUB increases ρ by the same rate 0.71 %. Similarly, ρ increases by 0.64 % and 0.74 %, 0.65 % and 0.74 %, respectively, on the addition of 0.0252 mol·kg−1 Sm(NO3)3 and Gd(NO3)3 to WC and WCB. Further, the ρ increased by
0.75 % and 0.74 %, 0.74 % and 0.76 %, respectively, on the addition of 0.0252 mol·kg−1 Sm(NO3)3 and Gd(NO3)3 to WCU and WCUB. It appears that the more increased ρ values when Ln(NO3)3 is added to WCB and WCUB than to WC are due to the higher charge density (CD) of lanthanide ions (Ln3+), which interact strongly with the excess water released to the bulk resulting from overlapping of BSA hydration sphere with C and U hydration spheres. In general, the ρ value are as Gd(NO3)3 > Sm(NO3)3 > Pr(NO3)3 with WC and WCU, while with WCB and WCUB, as Pr(NO3)3 > Gd(NO3)3 > Sm(NO3)3. These trends indicate that, in the presence of hydrophilic groups like −COO−, −OH, and >CO in WC and WCU, Gd3+ with highest CD results in development of strongest ion-hydrophilic interaction (IHI), while Pr3+ with lowest CD (Gd3+ = 5.22 nC·m−1, Sm3+ = 5.00 nC·m−1, and Pr3+ = 4.75 nC·m−1)32 results in the development of weakest IHI. Similarly, with WCB and WCUB, there is a dominance of ionhydrophobic interaction (IHbI) over IHI for Gd3+, whereas there is a dominance of IHI over IHbI for Pr3+. The development of stronger IHI increases the IP, while the dominance of IHbI over IHI decreases the IP. 3.2. Apparent Molar Volume (Vϕ). Densities of Ln(NO3)3 with WC, WCU, WCB, and WCUB at T = 298.15 K have been used to calculate the apparent molar volume, Vϕ, of Pr(NO3)3, Sm(NO3)3, and Gd(NO3)3 from the equation given below:33 3646
dx.doi.org/10.1021/je5005388 | J. Chem. Eng. Data 2014, 59, 3643−3651
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1000(ρ0 − ρ) mρ0 ρ
+
Article
M ρ
(1) −1
where m is the molality of Ln(NO3)3 (mol·kg ), ρ0 and ρ are densities (g·cm−3) of solvent and solution, respectively, and M is the molar mass (g·mol−1) of Ln(NO3)3. The obtained Vϕ values are given in Tables 2 to 4, and their concentration dependence are illustrated in Figures 1 to 4, where the curves
Figure 4. Effect of concentration on apparent molar volume of Pr(NO3)3 (□), Sm(NO3)3 (■), and Gd(NO3)3 (△) with WCUB at 298.15 K.
where Sv is the experimental slope portraying nature of solute− solute interactions (S LSLI), while V ϕ0 is the intercept representing nature of solute−solvent interactions (SLSOI)35 and are given in Table 5. The V0ϕ values for Pr(NO3)3, Sm(NO3)3, and Gd(NO3)3 follow the order: WCUB < WCB < WCU < WC and are positive. The positive V0ϕ indicate that SLSOI such as ion−hydrophilic interactions are dominant over the ion−hydrophobic interactions. The lower V0ϕ values of Ln3+ with (WCU and WCB) and WCUB than the corresponding values with WC and WCU, respectively, could be due to the following interactions given below: a. Ion−hydrophilic interaction (IHI) among the Ln3+ and NO3− ions and hydrophilic groups (−COO−, −OH, −NH2, NH3+, and >CO) of C, U, and BSA. This weakens the electrostriction resulting in increased V0ϕ values.36 b. Ion−hydrophobic interactions (IHbI) occurring among Ln3+ and NO3− ions and nonpolar groups (−CH2/hydrophobic domain) of C and BSA. This interaction strengthens the electrostriction resulting in decreased V0ϕ values.36 These results indicate the development of HHI between hydrophilic −NH2 and >CO of U and −COOH and −OH of C and, in doing so, reduces the IHI between Ln3+ and C since less hydrophilic domains are now available on C to interact with Ln3+. Due to this shielding of IHI by U, the IHI between Ln3+ and C in the presence of U seems to be weaker than the IHI in its absence resulting in V0ϕ value with WCU < WC and similarly the V0ϕ value with WCUB < WCB. On the contrary, the addition of BSA to WC increases the hydrophobicity, and as a result, the IHbI existing among Ln3+ and NO 3 − ions and nonpolar groups (−CH 2 /hydrophobic domains) of C and BSA, dominates over the IHI, causing V0ϕ values with WCB < WC. Similarly, the increased hydrophobicity in WCUB due to hydrophobic domains of BSA causes domination of IHbI over IHI, resulting in V0ϕ values with WCUB < WCU. The IHbI strengthens the electrostriction of water molecules in the solutions. Thus, the hydrated Ln3+ attracts some water molecules from the bulk with a decrease in volume. The trend of variation in V0ϕ values for Ln(NO3)3 with WC and WCB are as Gd(NO3)3 > Sm(NO3)3 > Pr(NO3)3 and depicts strongest IHI with C in case of Gd(NO3)3 where the water electrostriction are weakened in a more effective way: subsequently the strongest SLSOI with the weakest SLSLI. These result in the relaxation of greater amount of water molecules to the bulk from the hydrated Gd3+, leading to its higher V0ϕ values than Sm(NO3)3 and Pr(NO3)3. Further, the variations in V0ϕ values for Ln(NO3)3 with WCU and WCUB are as Pr(NO3)3 > Sm(NO3)3 > Gd(NO3)3, suggesting greater dominance of IHbI
Figure 1. Effect of concentration on apparent molar volume of Pr(NO3)3 (□), Sm(NO3)3 (■), and Gd(NO3)3 (△) with WC at 298.15 K.
Figure 2. Effect of concentration on apparent molar volume of Pr(NO3)3 (□), Sm(NO3)3 (■), and Gd(NO3)3 (△) with WCB at 298.15 K.
Figure 3. Effect of concentration on apparent molar volume of Pr(NO3)3 (□), Sm(NO3)3 (■), and Gd(NO3)3 (△) with WCU at 298.15 K.
are typical for Ln(NO3)3 with WCB and WCUB, whereas with WC and WCU are unique. The apparent molar volumes at infinite dilution of Ln(NO3)3, V0ϕ, were obtained by leastsquares fitting of experimental data to the following equation:34 Vϕ = V ϕ0 + Svm1/2 + Bv m
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Table 5. Limiting Apparent Molal Volume V0ϕ and Slope Sv and Bv of Pr(NO3)3, Sm(NO3)3, and Gd(NO3)3 with WC, WCB, WCU, and WCUB at T = 298.15 K V0ϕ/ 10−6 m3·mol−1
Sv/10−6 kg1/2·m3·mol−3/2
Bv/10−6 kg·m3·mol−2
WC Pr(NO3)3 Sm(NO3)3 Gd(NO3)3
227.34 ± 2.13 245.97 ± 2.24 253.81 ± 2.27
Pr(NO3)3 Sm(NO3)3 Gd(NO3)3
125.81 ± 1.51 133.71 ± 0.75 148.23 ± 0.22
Pr(NO3)3 Sm(NO3)3 Gd(NO3)3
188.66 ± 2.09 176.65 ± 1.48 168.28 ± 2.77
Pr(NO3)3 Sm(NO3)3 Gd(NO3)3
112.18 ± 1.56 109.22 ± 1.59 105.38 ± 1.57
−444.31 ± 11.67 −506.59 ± 12.29 −554.48 ± 12.47
715.66 ± 16.94 809.43 ± 17.82 902.11 ± 18.09
153.57 ± 7.59 134.98 ± 7.06 75.10 ± 2.18
−103.76 ± 10.39 −41.84 ± 8.48 42.01 ± 0.43
−288.42 ± 13.09 −176.90 ± 6.19 −118.09 ± 16.10
571.06 ± 24.12 385.02 ± 6.79 285.43 ± 24.21
257.51 ± 7.98 294.22 ± 36.92 310.58 ± 8.00
−347.07 ± 11.08 −352.38 ± 11.22 −349.09 ± 11.12
WCB
WCU
WCUB
over IHI for Gd3+. It seems that U develops HHI with C on its inclusion to WC and WCB, thereby decreasing the IHI between Ln3+ and C. Due to this shielding effect by U on IHI, the IHbI between Ln3+ and C tends to dominate over IHI where Gd3+ due to its highest CD develops the strongest, while Pr3+ develops the weakest IHbI with the strongest SLSOI and weakest SLSLI. These results are excellently supported by the Sv values (Table 5) which follows as Pr(NO3)3 > Sm(NO3)3 > Gd(NO3)3 with WC and WCB, while Gd(NO3)3 > Sm(NO3)3 > Pr(NO3)3 with WCU and WCUB. Further, the higher Sv values with WCB and WCUB than those with WC and WCU supports the development of stronger SLSLI induced by BSA. Figure S1 in the Supporting Information illustrates that, in the presence of U and with increasing CD of the Ln3+, the rate of decrease in V0ϕ with WC drops by 23.38 %. Similarly, in the presence of BSA and with increasing CD of the Ln3+, the rate of increase in V0ϕ with WC decreases by 16.56 %, while with WCU it decreases by 66.85 %. This infers that the inclusion of U in WC increases the IHbI by 23.38 %, while BSA addition to WC increases the IHbI by 16.56 %. It is interesting to see the impact of U, where the IHbI increases from 16.56 % to 43.47 % on BSA addition in its presence in WCU, thereby showing the advancement of stronger IHbI in the presence of U. Table 5 shows that Bv values for Ln(NO3)3 with WC and WCU follows as Gd(NO3)3 > Sm(NO3)3 > Pr(NO3)3, while with WCU and WCUB as Gd(NO3)3 < Sm(NO3)3 < Pr(NO3)3. In absence of U, the highest Bv values for Gd3+ indicate the presence of strongest electrostatic interactions (IHI), while the least Bv values for Gd3+ in the presence of U indicates the presence of strongest nonelectrostatic interactions (IHbI).37 BSA being a macromolecule has n numbers of interacting domains. When these molecular species are dispersed in a polar medium like WC and WCU, the various interaction modes are applicable to monitor its interactions with Ln3+ in the presence of C and U because they hinders the approach of Ln3+ toward the polar sites of BSA. The BSA causes alignment of C and U hydration spheres around itself, which are rearranged in the presence of Ln3+, thereby changing the overall volume. Thus, an additional volume change in these interactions is generated and is noted as apparent molar transfer volume, ΔtrV0ϕ. The apparent molar transfer volumes of Ln(NO3)3 from WC to
WCB, WCU, and WCUB, reported in Table S2 of Supporting Information, were obtained from the equation: Δtr V ϕ0 = V ϕ0(with WCU/WCB/WCUB) − V ϕ0(with WC)
(3)
ΔtrV0ϕ
In general, variation in the inferred expansion or contraction in the size of the hydration sphere around the Ln3+. From Table S2 of the Supporting Information, it is evident that ΔtrV0ϕ values of Ln(NO3)3 from WC to WCB, WCU, and WCUB are negative. The negative ΔtrVϕ0 values can be explained by the fact that Ln3+ interacts indirectly with the −COO− and −OH of C in the presence of U and −NH3+, −COO−, and >CO of BSA in the presence of C and U, thereby leading to a volumetric increase in the electrostriction of the solvent. The ΔtrV0ϕ value of Ln(NO3)3 is noted as WCUB < WCB < WCU. The higher ΔtrV0ϕ value of Ln(NO3)3 can be attributed to the higher magnitude of reduction of electrostricted water molecules along C in case of WCU than in WCB and WCUB. The trends of variation of ΔtrV0ϕ are consistent with the trends of variation of V0ϕ. The contribution of intrinsic volume of solute and volume change due to solute interactions with solvent to the V0ϕ value can be illustrated through the following equation38 V ϕ0 = Vintrinsic − Vshrinkage
(4)
If it is assumed that the magnitude of Vintrinsic remains of the same magnitude in WC and WCU/WCB/WCUB, the negative ΔtrV0ϕ for the Ln(NO3)3 can be explained in terms of an increase in the shrinkage volume in the presence of U and BSA molecules. On BSA addition to WC, the 16.56 % increment in IHbI occurring among Ln3+, NO3− ions, and nonpolar groups BSA causes the electrostriction of the neighboring water molecules due to the charged Ln3+ centers to increase, thereby increasing the shrinkage volume with negative ΔtrV0ϕ values. Since U results in the development of HHI between its >CO and −COO−, −OH of C, suppressing the IHI between Ln3+ and −COO−, −OH, >CO of C and U, its presence elevates the IHbI to 43.47 % on BSA inclusion to WCU. This high increase in IHbI causes the electrostriction of the neighboring water molecules to increase the maximum with highest increase in the shrinkage volume and most negative ΔtrV0ϕ. The inclusion of U in WC increases the IHbI by 23.38 % but is to 3648
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Table 6. Viscosity B-Coefficients and A-Coefficients for Pr(NO3)3, Sm(NO3)3, and Gd(NO3)3 with W, WC, WCB, WU, WCU, and WCUB at T = 298.15 K Pr(NO3)3
Sm(NO3)3
Gd(NO3)3
WC B/kg·mol−1 A/kg1/2·mol−1/2
0.6668 ± 0.0129 0.0003 ± 0.0068
B/kg·mol−1 A/kg1/2·mol−1/2
0.4442 ± 0.0125 0.0572 ± 0.0067
B/kg·mol−1 A/kg1/2·mol−1/2
0.8425 ± 0.0123 −0.0014 ± 0.0065
B/kg·mol−1 A/kg1/2·mol−1/2
0.5900 ± 0.0122 0.0116 ± 0.0064
0.6702 ± 0.0137 0.0039 ± 0.0072
0.6777 ± 0.0116 0.0064 ± 0.0061
0.5247 ± 0.0109 0.0162 ± 0.0060
0.5675 ± 0.0111 0.0001 ± 0.0061
0.71082 ± 0.0217 −0.0013 ± 0.0115
0.7024 ± 0.0126 0.0068 ± 0.0068
0.5608 ± 0.0125 0.0118 ± 0.0066
0.4944 ± 0.0121 0.0250 ± 0.0064
WCB
WCU
WCUB
an extent neutralized by the presence of IHI between Ln3+ and >CO, −COO−, −OH of C and U. The IHbI are also obscured in the absence of a large hydrophobic domain in WCU. This results in electrostriction of the neighboring water molecules to increase the minimum with least increase in the shrinkage volume and least negative ΔtrV0ϕ values. 3.3. Viscosity (η). Viscosities of Ln(NO3)3:Pr(NO3)3, Sm(NO3)3, and Gd(NO3)3 with WC, WCB, WCU, and WCUB as a function of their molalities at T = 298.15 K, are summarized in Tables 2 to 4, illustrated in Figures S2 to S5 in Supporting Information, where η values increase with concentration. A perusal of Table 2 reveals that η values of aqueous solvent mixtures are as WCUB > WCB > WCU > WC. The η values of WCB and WCU are 1.87 % and 0.06 % higher than the viscosity of WC, while for WCUB is 2.20 % higher than the viscosity of WCU. The experimental results of relative viscosity data (ηr) of Ln(NO3)3 with WC, WCB, WCU, and WCUB have been analyzed using the Jones−Dole equation, given below:39 ηr = η /η0 = 1 + Am1/2 + Bm
Figure 5. Effect of solvent on B-coefficient with Pr(NO3)3 (□), Sm(NO3)3 (■), and Gd(NO3)3 (△) at 298.15 K.
to weaker interaction between Ln3+ and solvent (SLSOI) and development of stronger SLSLI with decreased B values in the presence of U and BSA. The lowest B values for Gd3+ with WCU and WCUB could be due to the presence of weaker IHI prevailing between Gd3+ and −COO−/−OH/−NH2/NH3+/ >CO of C, U, and BSA because Gd3+ due to its highest CD develops strongest IHbI and the weakest IHI in vicinity of U. This trend is further supported by the Sv values (Table 5) with WCU and WCUB, noted as Gd(NO3)3 > Sm(NO3)3 > Pr(NO3)3 with increased SLSLI. The highest B values for Gd3+ with WC and WCB could be due to the dominance of IHI prevailing between Gd3+ and −COO−/−OH//NH3+/>CO of C and BSA because Gd3+ due to its highest CD develops the strongest IHI and the weakest IHbI in the absence of U. This trend is further supported by the Sv values (Table 5) with WC and WCB noted as Gd(NO3)3 < Sm(NO3)3 < Pr(NO3)3 with increased SOSLI. Thus, the structure-breaking tendency of the Ln(NO3)3 follows the order Gd(NO3)3 > Sm(NO3)3 > Pr(NO3)3 in the absence of U, while the structure breaking tendency of the Ln(NO3)3 follows the order Gd(NO3)3 < Sm(NO3)3 < Pr(NO3)3 in the presence of U. 3.4. Surface Tension (γ). Surface tension (γ) values of Ln(NO3)3 with WC, WCB, WCU, and WCUB are listed in Tables 2 to 4 and illustrated in Figures S6 to S9 in the Supporting Information. The surface tension of solvent mixtures are as WCU > WC > WCUB > WCB and could be due to the strengthening of IMF between U and W, on U addition to WC and WCB. The addition of BSA to WC and WCU increases the hydrophobicity of the medium, thereby weakening the HB existing between water molecules with decreased γ values. The extent of HHI with water is increased
(5)
where η and η0 are the viscosities of the solution and solvent, respectively, and m is the molal concentration. A is the Falkenhagen constant specific of SLSLI,40,41 and B is viscosity Bcoefficient and is a measure of structural modifications induced by SLSOI.42−44 The plots of [ηr − 1]/m1/2 versus m1/2 for Ln(NO3)3 are linear. The values of A and B parameters have been calculated from least-square fit on fitting the experimental results in the Jones−Dole equation (eq 5), and these values along with their standard uncertainties are reported in Table 6. Figure 5 illustrates the impact of solvents on the B values for Ln(NO3)3. The A-coefficient values reflect long-range interionic forces (SLSLI) which decreases when SLSOI such as ion− hydrophilic interactions dominates over the ion−hydrophobic interactions, reflected by higher B-values. The viscosity Bcoefficient is a valuable tool providing information regarding the solvation of solutes and their effect on the structure of the solvent in the vicinity of the solute molecule. A perusal of Table 6 shows that the B values are positive for all Ln3+, which with their increasing CD, increases in the absence and decreases in the presence of U. Additionally, for the Ln3+, the B values decreases on BSA introduction to WC and WCU. Findings from V0ϕ shows that, with increasing CD of Ln3+, the inclusion of BSA in WC increases the IHbI by 16.56 %, and the inclusion of U in WC increases the IHbI by 23.38 %, while its presence in WCU elevates the IHbI to 43.47 % on BSA inclusion. This leads 3649
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in the presence of U leading to the γ value as WCB < WCUB. The γ values for Ln(NO3)3 with WC and WCU increase with the concentration (Figures S6 and S8) and follows the order Gd(NO3)3 > Sm(NO3)3 > Pr(NO3)3. Gd3+ due to its highest CD may form strongest IHI with water, thereby strengthening the IMF with water molecules and the highest γ value, while Pr3+ due to its lowest CD develops weaker IMF with the lowest γ value. With increasing Ln(NO3)3 concentration and in the absence of BSA (Figures S6 and S8), the γ values increase owing to the increased IMF due to increased IHI with water. Interestingly, with WCB and WCUB, the γ values are found to decrease with increasing Ln(NO3)3 concentration (Figures S7 and S9) and may be due to the increased IHI with BSA disrupting the HB and Coulombic interaction (between −NH3+ and −COO−) within the BSA molecules. This leads to the dominance of IHbI over IHI with BSA, leading to decreased γ values. With WCB, the γ values for the Ln(NO3)3 follow the order Sm(NO3)3 < Gd(NO3)3 < Pr(NO3)3 and could be explained by the dominance of IHI over the weakest IHbI prevailing between Pr3+ and hydrophobic domains of BSA. With WCUB, the abrupt γ trend observed for Ln(NO3)3 may be due to nonhomogeneous redistribution of electronic clouds over the BSA molecules in the presence of U.
ASSOCIATED CONTENT
S Supporting Information *
Supporting tables and figures. This material is available free of charge via the Internet at http://pubs.acs.org.
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REFERENCES
(1) Peng, L.; Hongyu, X.; Xi, L.; Lifang, R.; Chaocan, Z. Calorimetric study of nonspecific interaction between lead ions and bovine serum albumin. Biol. Trace Elem. Res. 2007, 118, 97−103. (2) Olson, R. E.; Christ, D. D. Plasma protein binding of drugs. Annu. Rep. Med. Chem. 1996, 31, 327−336. (3) Kragh-Hansen, U. Molecular aspects of ligand binding to serum albumin. Pharmacol. Rev. 1981, 33, 17−53. (4) Yan, J. K.; Cai, P. F.; Cao, X. Q.; Fan, T. T.; Ma, H. L. Studies on interaction of polysaccharide-templated silver nanoparticles with bovine serum albumin. J. Inorg. Organomet Polym. 2013, 23, 1383− 1388. (5) Guan, M.; Tao, F.; Sun, J.; Xu, Z. Facile preparation method for rare earth phosphate hollow spheres and their photoluminescence properties. Langmuir 2008, 24, 8280−8283. (6) Yan, R.; Sun, X.; Wang, X.; Peng, Q.; Li, Y. Crystal structures, anisotropic growth, and optical properties: controlled synthesis of lanthanide orthophosphate one-dimensional nanomaterials. Chem. Eur. J. 2005, 11, 2183−2195. (7) Wang, G.; Peng, Q.; LI, Y. Lanthanide-doped nanocrystals: synthesis, optical-magnetic properties, and applications. Acc. Chem. Res. 2011, 44, 322−332. (8) Jongmin, S.; Anisur, R. M.; Mi, K. K.; Im, G. H.; Lee, J. H.; Lee, I. S. Hollow manganese oxide nanoparticles as multifunctional agents for magnetic resonance imaging and drug delivery. Angew. Chem., Int. Ed. 2009, 48, 321−324. (9) Xin, L.; Biao, X.; Simin, K.; Wang, X. Multi-functionalized inorganic−organic rare earth hybrid microcapsules. Adv. Mater. 2008, 20, 3739−3744. (10) Dong, F.; Guo, W.; Bae, J. H.; Ha, C. S. Highly porous, watersoluble, superparamagnetic, and biocompatible magnetite nanocrystal clusters for targeted drug delivery. Chem.Eur. J. 2011, 17, 12802− 12808. (11) Huang, C. C.; Liu, T. Y.; Su, C. H.; Lo, Y. W.; Chen, J. H.; Yeh, C. H. Superparamagnetic hollow and paramagnetic porous Gd2O3 particles. Chem. Mater. 2008, 20, 3840−3848. (12) Liu, Y.; Tu, D.; Zhua, H.; Chen, X. Lanthanide-doped luminescent nanoprobes: controlled synthesis, optical spectroscopy, and bioapplications. Chem. Soc. Rev. 2013, 42, 6924−6958. (13) Yoon, Y. S.; Lee, B.; Lee, K. S.; Im, G. H.; Byeon, S. H.; Lee, J. H.; Lee, I. S. Surface modification of exfoliated layered gadolinium hydroxide for the development of multimodal contrast agents for MRI and fluorescence imaging. Adv. Funct. Mater. 2009, 19, 3375−3380. (14) Gierada, D. S.; Bae, K. T. Gadolinium as a CT contrast agent: Assessment in a porcine model. Radiology 1999, 210, 829−834. (15) Herborn, C. U.; Honold, E.; Wolf, M.; Kemper, J.; Kinner, S.; Adam, G.; Barkhausen, J. Clinical safety and diagnostic value of the gadolinium chelate gadoterate meglumine (Gd-DOTA). Invest. Radiol. 2007, 42, 58−62. (16) Zhang, M.; Shi, S.; Meng, J.; Wang, X.; Fan, H.; Zhu, Y.; Wang, X.; Qian, Y. Preparation and characterization of near-infrared luminescent bifunctional core/shell nanocomposites. J. Phys. Chem. C 2008, 112, 2825−2830. (17) Xu, M.; Ma, Z. R.; Huang, L.; Chen, F. J.; Zeng, Z. Z. Spectroscopic studies on the interaction between Pr(III) complex of an ofloxacin derivative and bovine serum albumin or DNA. Spectrochim. Acta, Part A 2011, 78, 503−511. (18) Ahmad, M. W.; Kim, C. R.; Baeck, J. S.; Chang, Y.; Kim, T. J.; Bae, J. E.; Chae, K. S.; Lee, G. H. Bovine serum albumin (BSA) and cleaved-BSA conjugated ultrasmall Gd2O3 nanoparticles: Synthesis, characterization, and application to MRI contrast agents. Colloids Surf., A 2014, 450, 67−75. (19) Tsoli, M.; Kuhn, H.; Brandau, W.; Esche, H.; Schmid, G. Cellular uptake and toxicity of Au55 clusters. Small 2005, 1, 841−844. (20) Pan, Y.; Neuss, S.; Leifert, A.; Fischler, M.; Wen, F.; Simon, U.; Schmid, G.; Brandau, W.; Jahnen, D. W. Size-dependent cytotoxicity of gold nanoparticles. Small 2007, 3, 1941−1949.
4. CONCLUSION The positive values of V0ϕ for Ln(NO3)3 with WC, WCB, WCU, and WCUB indicated that interactions such as ion-hydrophilic interactions are dominant over ion-hydrophobic interactions. The V0ϕ values are found to be affected by charge density of the Ln3+ and follow the order Gd(NO3)3 > Sm(NO3)3 > Pr(NO3)3 with WC and WCB, while the Pr(NO3)3 > Sm(NO3)3 > Gd(NO3)3 is with WCU and WCUB. This confirms the prevalence of strongest IHI and IHbI between C and Gd3+ in the absence and presence of U, respectively. The negative ΔtrV0ϕ values for Pr(NO3)3, Sm(NO3)3, and Gd(NO3)3 further confirms the dominance of IHbI over IHI in the presence of BSA while weakening of IHI in the presence of U. These findings additionally are in good agreements with the B values where the order is same as for V0ϕ values. Moreover, the lower B values with WCB and WCUB than with WC and WCU establish the fact that BSA acts as a structure maker. In the absence of U, Gd(NO3)3 have been found to have the strongest structure breaker tendency, whereas in its presence it is found to have the strongest structure-making tendency.
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The authors are grateful to the Vice Chancellor, Central University of Gujarat, Gandhinagar-382030, India, for financial and infrastructural support for this research work. Notes
The authors declare no competing financial interest. Author e-mail:
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[email protected]. 3650
dx.doi.org/10.1021/je5005388 | J. Chem. Eng. Data 2014, 59, 3643−3651
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(42) Kay, R. L.; Vituccio, T.; Zawoyski, C.; Evans, D. F. Viscosity B coefficients for the tetraalkylammonium halides. J. Phys. Chem. 1966, 70, 2336−2341. (43) Jenkins, H. D. B.; Marcus, Y. Viscosity B-coefficients of ions in solution. Chem. Rev. 1995, 95, 2695−2724. (44) Chandra, A.; Patidar, V.; Singh, M.; Kale, R. K. Physicochemical and friccohesity study of glycine, L-alanine and L-phenylalanine with aqueous methyltrioctylammonium and cetylpyridinium chloride from T = (293.15 to 308.15) K. J. Chem. Thermodyn. 2013, 65, 18−28.
(21) Semmler-Behnke, M.; Kreyling, W. G.; Lipka, J.; Fertsch, S.; Wenk, A.; Takenaka, S.; Schmid, G.; Brandau, W. Biodistribution of 1.4- and 18-nm gold particles in rats. Small 2008, 4, 2108−2111. (22) Yen, H. J.; Hsu, S. H.; Tsai, C. L. Cytotoxicity and immunological response of gold and silver nanoparticles of different sizes. Small 2009, 5, 1553−1561. (23) Murdock, R. C.; Braydich-Stolle, L.; Schrand, A. M.; Hlager, J. J.; Hussain, S. M. Characterization of nanomaterial dispersion in solution prior to in vitro exposure using dynamic light scattering technique. Toxicol. Sci. 2008, 101, 239−253. (24) Grainger, D. W.; Castner, D. G. Nanobiomaterials and nanoanalysis: Opportunities for improving the science to benefit biomedical technologies. Adv. Mater. 2008, 20, 867−877. (25) Hussain, S. M.; Braydich-Stolle, L. K.; Schrand, A. M.; Murdock, R. C.; Yu, K. O.; Mattie, D. M.; Schlager, J. J.; Terrones, M. Toxicity evaluation for safe use of nanomaterials: Recent achievements and technical challenges. Adv. Mater. 2009, 21, 1549−1559. (26) Naidu, K. T.; Prabhu, N. P. Protein−Surfactant Interaction: Sodium Dodecyl Sulfate-Induced Unfolding of Ribonuclease A. J. Phys. Chem. B 2011, 115, 14760−14767. (27) Quintanar, L.; Rivillas-Acevedo, L. Studying metal ion-protein interactions: electronic absorption, circular dichroism, and electron paramagnetic resonance. Methods Mol. Biol. 2013, 1008, 267−297. (28) Jacobson, K. B.; Turner, J. E. The interaction of cadmium and certain other metal ions with proteins and nucleic acids. Toxicology 1980, 16, 1−37. (29) Buranaprapuk, A.; Leach, S. P.; Kumar, C. V.; Bocarsly, J. R. Protein cleavage by transition metal complexes bearing amino acid substituents. Biochim. Biophys. Acta 1998, 8, 309−316. (30) Rashid, F.; Sharma, S.; Bano, B. Comparison of guanidine hydrochloride (GdnHCl) and urea denaturation on inactivation and unfolding of human placental cystatin (HPC). Protein J. 2005, 24, 283−292. (31) Singh, M. Survismeter type I and II for surface tension, viscosity measurements liquids for academic, research and development studies. J. Biochem. Biophys. Methods 2006, 67, 151−161. (32) Chemistry, Part I, Textbook for class XII, The d- and f-block elements; N.C.E.R.T.: New Delhi, 2006; pp 227−230. (33) Ayranci, E. Apparent molar volume and viscosity of compounds with asymmetric carbon atoms. J. Chem. Eng. Data 1997, 42, 934−937. (34) Masson, D. O. Solute molecular volumes in relation to solvation and ionization. Philos. Mag. 1929, 8, 218−235. (35) Rodríguez, H.; Soto, A.; Arce, A.; Khoshkbarchi, M. K. Apparent molar volume, isentropic compressibility, refractive index, and viscosity of DL-Alanine in aqueous NaCl solutions. J. Solution Chem. 2003, 32, 53−63. (36) Desnoyers, J. E.; Arel, M.; Perron, G.; Jolicoeur, C. Apparent molal volumes of alkali halides in water at 25.deg. Influence of structural hydration interactions on the concentration dependence. J. Phys. Chem. 1969, 73, 3346−3351. (37) Shekaari, H.; Armanfar, E. Physical Properties of Aqueous Solutions of Ionic Liquid, 1-Propyl-3-methylimidazolium Methyl Sulfate, at T = (298.15 to 328.15) K. J. Chem. Eng. Data 2010, 55, 765−772. (38) Franks, F.; Quickenden, M. A. j.; Reid, D. S.; Watson, B. Calorimetric and volumetric studies of dilute aqueous solutions of cyclic ether derivatives. Trans. Faraday Soc. 1970, 66, 582−589. (39) Jones, G.; Dole, M. The viscosity of aqueous solutions of strong electrolytes with special reference to barium chloride. J. Am. Chem. Soc. 1929, 51, 2950−2964. (40) Falkenhagen, H.; Vernon, E. L. The viscosity of strong electrolyte solutions according to electrostatic theory. Philos. Mag. 1932, 14, 537−565. (41) Feakins, D.; Freemantle, D. J.; Lawrence, K. G. Transition state treatment of the relative viscosity of electrolytic solutions. Applications to aqueous, non-aqueous and methanol + water systems. J. Chem. Soc., Faraday Trans. 1 1974, 70, 795−806. 3651
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