Journal of Biological Physics

, Volume 44, Issue 3, pp 345–360 | Cite as

Laser interferometry of the hydrolytic changes in protein solutions: the refractive index and hydration shells

  • R. M. SarimovEmail author
  • T. A. Matveyeva
  • V. N. Binhi
Original Paper


Using an original laser interferometer of enhanced sensitivity, an increase in the refractive index of a protein solution was observed during the reaction of proteolysis catalyzed by pepsin. The increase in the refractive index of the protein solution at a concentration of 4 mg/ml was \( 9 \times 10^{-6} \) for bovine serum albumin and \(2.4 \times 10^{- 6}\) for lysozyme. The observed effect disproves the existing idea that the refractive index of protein solutions is determined only by their amino acid composition and concentration. It is shown that the refractive index also depends on the state of protein fragmentation. A mathematical model of proteolysis and a real-time method for estimating the state of protein hydration based on the measurement of refractive index during the reaction are proposed. A good agreement between the experimental and calculated time dependences of the refractive index shows that the growth of the surface of protein fragments and the change in the number of hydration cavities during proteolysis can be responsible for the observed effect.


Enzymatic proteolysis Optical methods in biochemistry Mathematical model Computer simulation 


Compliance with Ethical Standards

Declaration of interest

The authors report no conflicts of interest.

Supplementary material

10867_2018_9494_MOESM1_ESM.pdf (549 kb)
(PDF 548 KB)


  1. 1.
    McMeekin, T.L., Wilensky, M., Groves, M.L.: Refractive indices of proteins in relation to amino acid composition and specific volume. Biochem. Biophys. Res. Commun. 7(2), 151 (1962). CrossRefGoogle Scholar
  2. 2.
    McMeekin, T.L., Groves, M.L., Hipp, N.J.: Refractive indices of amino acids, proteins, and related substances. Adv. Chem. Ser. 1, 54 (1964). CrossRefGoogle Scholar
  3. 3.
    Zhao, H., Brown, P.H., Schuck, P.: On the distribution of protein refractive index increments. Biophys. J. 100(9), 2309 (2011). ADSCrossRefGoogle Scholar
  4. 4.
    Barer, R., Joseph, S.: Refractometry of living cells. J. Cell Sci. 3(32), 399 (1954)Google Scholar
  5. 5.
    Zhao, H., Brown, P.H., Magone, M.T., Schuck, P.: The molecular refractive function of lens \(\gamma \)-crystallins. J. Mol. Biol. 411(3), 680–699 (2011). CrossRefGoogle Scholar
  6. 6.
    Ball, V., Ramsden, J.J.: Buffer dependence of refractive index increments of protein solutions. Biopolymers 46(7), 489 (1998).<489::aid-bip6>;2-e CrossRefGoogle Scholar
  7. 7.
    Cole, T., Kathman, A., Koszelak, S., McPherson, A.: Determination of local refractive index for protein and virus crystals in solution by mach-zehnder interferometry. Anal. Biochem. 231(1), 92 (1995). CrossRefGoogle Scholar
  8. 8.
    Yin, D.C., Inatomi, Y., Luo, H.M., Li, H.S., Lu, H.M., Ye, Y.J., Wakayama, N.I.: Interferometry measurement of protein concentration evolution during crystallization and dissolution with improved reliability and versatility. Meas. Sci. Technol. 19(4), 045303 (2008)ADSCrossRefGoogle Scholar
  9. 9.
    Voros, J.: The density and refractive index of adsorbing protein layers. Biophys. J. 87(1), 553 (2004). ADSCrossRefGoogle Scholar
  10. 10.
    Markov, D.A., Swinney, K., Bornhop, D.J.: Label-free molecular interaction determinations with nanoscale interferometry. J. Am. Chem. Soc. 126(50), 16659 (2004). CrossRefGoogle Scholar
  11. 11.
    Jepsen, S.T., Jorgensen, T.M., Zong, W., Trydal, T., Kristensen, S.R., Sorensen, H.S.: Evaluation of back scatter interferometry, a method for detecting protein binding in solution. The Analyst (Royal Society of Chemistry) 140(3), 895 (2015). ADSGoogle Scholar
  12. 12.
    Kabashin, A.V., Nikitin, P.I.: Surface plasmon resonance interferometer for bio- and chemical-sensors. Opt. Commun. 150(1–6), 5 (1998). ADSCrossRefGoogle Scholar
  13. 13.
    Homola, J.: Surface plasmon resonance sensors for detection of chemical and biological species. Chem. Rev. 108(2), 462 (2008). CrossRefGoogle Scholar
  14. 14.
    Binhi, V.N., Sarimov, R.M.: Relaxation of liquid water states with altered stoichiometry. Biophysics 59(4), 515 (2014). CrossRefGoogle Scholar
  15. 15.
    Sarimov, R.M., Matveyeva, T.A., Vasin, A.L., Binhi, V.N.: Changes in the refractive index of a solution during proteolysis of bovine serum albumin with pepsin. Biophysics 62(2), 177 (2017). CrossRefGoogle Scholar
  16. 16.
    Srividhya, J., Schnell, S.: Why substrate depletion has apparent first-order kinetics in enzymatic digestion. Comput. Biol. Chem. 30(3), 209 (2006). CrossRefzbMATHGoogle Scholar
  17. 17.
    Bull, H.B., Currie, B.T.: Peptic hydrolysis of egg albumin. I. Kinetic studies. J. Am. Chem. Soc. 71(8), 2758 (1949)CrossRefGoogle Scholar
  18. 18.
    Sachdev, G.P., Fruton, J.S.: Kinetics of action of pepsin on fluorescent peptide substrates. Proc. Natl. Acad. Sci. U.S.A. 72(9), 3424 (1975)ADSCrossRefGoogle Scholar
  19. 19.
    Born, M., Wolf, E.: Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light, 7th edn. Cambridge University Press, Cambridge (1999)CrossRefzbMATHGoogle Scholar
  20. 20.
    Zangi, R., Hagen, M., Berne, B.J.: Effect of ions on the hydrophobic interaction between two plates. J. Am. Chem. Soc. 129(15), 4678 (2007). CrossRefGoogle Scholar
  21. 21.
    Tanford, C., Buzzell, J.G., Rands, D.G., Swanson, S.A.: The reversible expansion of bovine serum albumin in acid solutions. J. Am. Chem. Soc. 77(24), 6421 (1955). CrossRefGoogle Scholar
  22. 22.
    Keil, B.: Specificity of Proteolysis. Springer-Verlag, Berlin (1992)CrossRefGoogle Scholar
  23. 23.
    Gasteiger, E., Hoogland, C., Gattiker, A., Duvaud, S., Wilkins, M.R., Appel, R.D., Bairoch, A.: Protein identification and analysis tools on the ExPASy server. In: Walker, J.M. (ed.) The Proteomics Protocols Handbook, pp. 571–607. Humana Press, New Jersey (2005)Google Scholar
  24. 24.
    Beaven, G.H., Holiday, E.R.: Ultraviolet absorption spectra of proteins and amino acids. Adv. Protein Chem. 7, 319 (1952). CrossRefGoogle Scholar
  25. 25.
    Hayashi, K., Imoto, T., Funatsu, M.: Proteolysis of lysozyme-substrate complex. J. Fac. Agric. Kyushu Univ. 15, 387 (1969)Google Scholar
  26. 26.
    Dalgalarrondo, M., Dufour, E., Chobert, J.M., Bertrand-Harb, C., Haertle, T.: Proteolysis of \(\beta \)-lactoglobulin and \(\beta \)-casein by pepsin in ethanolic media. Int. Dairy J. 5(1), 1 (1995)CrossRefGoogle Scholar
  27. 27.
    Tam, J.J., Whitaker, J.R.: Rates and extents of hydrolysis of several caseins by pepsin, rennin, endothia parasitica protease and mucor pusillus protease. J. Dairy Sci. 55(11), 1523 (1972). CrossRefGoogle Scholar
  28. 28.
    Reddy, I.M., Kella, N.K., Kinsella, J.E.: Structural and conformational basis of the resistance of \(\beta \)-lactoglobulin to pectic and chymotryptic digestion. J. Agric. Food Chem. 36(4), 737 (1988). CrossRefGoogle Scholar
  29. 29.
    Schiebener, P., Straub, J., Levelt Sengers, J.M.H., Gallagher, J.S.: Refractive index of water and steam as function of wavelength, temperature and density. J. Phys. Chem. Ref. Data 19(3), 677 (1990). ADSCrossRefGoogle Scholar
  30. 30.
    Harvey, A.H., Kaplan, S.G., Burnett, J.H.: Effect of dissolved air on the density and refractive index of water. Int. J. Thermophys. 26(5), 1495 (2005). ADSCrossRefGoogle Scholar
  31. 31.
    Svergun, D.I., Richard, S., Koch, M.H.J., Sayers, Z., Kuprin, S., Zaccai, G.: Protein hydration in solution: Experimental observation by x-ray and neutron scattering. Proc. Natl. Acad. Sci. U.S.A. 95(5), 2267 (1998). ADSCrossRefGoogle Scholar
  32. 32.
    Sushko, O., Dubrovka, R., Donnan, R.S.: Sub-terahertz spectroscopy reveals that proteins influence the properties of water at greater distances than previously detected. J. Chem. Phys. 142(5), 055101 (2015)ADSCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media B.V., part of Springer Nature 2018

Authors and Affiliations

  1. 1.Prokhorov General Physics Institute of the Russian Academy of Sciences, GPI RASMoscowRussia
  2. 2.Faculty of BiologyLomonosov Moscow State UniversityMoscowRussia

Personalised recommendations