Bovine serum albumin observed by infrared spectrometry. I. Methodology, structural investigation, and water uptake

Abstract

The results of preliminary infrared (IR) spectrometry experiments on bovine serum albumin (BSA) films are presented. An analysis of spectral variations due to raising the temperature and deuteration of NH groups leads to the assignment of most IR bands of BSA. From this analysis we furthermore deduce that at 115°C only hydrogen bonds established by NH groups on the still present H2O molecules, which are so strongly bound to the protein that they do not evaporate, are weakened, some of which are broken. These NH⋮OH2 groups represent some 5% of all NH groups in the dried protein. Spectral changes due to hydration by water vapor are also analyzed and a precise method to measure the water‐vapor pressure of the atmosphere surrounding the BSA film, or equivalently the relative humidity, is described. Various procedures to measure the number of H2O molecules embedded in BSA are then presented and evaluated. One of them is selected as the best one for proteins, because it matches previous measurements based on gravimetric methods. This procedure is subsequently used in a study that is devoted to the determination of the various hydrogen‐bond configurations, or interaction configurations, which are adopted by H2O molecules during the various steps of hydration of BSA. This first analysis of hydration spectra allows the completion of the assignment of IR bands. The various spectral components of the amide I band, which are interchanged during the hydration process, cannot be assigned to various secondary structures, as is usually proposed. It suggests that this usual assignment should be used with care, especially by taking into account the state of hydration, when one wishes to obtain structural information from it. © 2000 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 62: 40–53, 2001

Hydrogen Bond Network of Water around Protein Investigated with Terahertz and Infrared Spectroscopy

“…Especially, the latter is strongly coupled with intermolecular HB dynamics (49)(50)(51)(52)(55)(56)(57)(58), and in general, the O-H stretching frequency red-shifts as the intermolecular HB becomes stronger (100)(101)(102)(103)(104). On the other hand, the complex dielectric constant of albumin crystal exhibits the several amide bands (66,105,106) between 30 and 50 THz, the C-H stretching (87 THz) (107), and N-H stretching (~100 THz) (66) in the MIR region. Hence, for the complex dielectric constant of albumin aqueous solution, the latter two stretching bands of albumin overlap with the O-H stretching of water, complicating the interpretation of the HB environment of water around protein.…”

Electrochemical impedance and spectroscopy study of the EDC/NHS activation of the carboxyl groups on poly(ε-caprolactone)/poly(m-anthranilic acid) nanofibers

“…On the contrary, after albumin immobilization onto nanofibers activated with 50/50 mM of EDC/NHS a broad peak was observed Guler and Sarac -eXPRESS Polymer Letters Vol.10, No.2 (2016) . The absorption in this region can be influenced by the contribution of water but in proteins the N-H groups are generally in greater numbers than O-H groups [27]. Also other albumin immobilized nanofibers showed no absorption at this region.…”

Albumin adsorption study onto hydroxyapatite-multiwall carbon nanotube based composites

“…The vibrational band seen at 2852 cm À1 represents eCH stretching, which is associated with pure BSA. The stretching bands at 1653 cm À1 and 1560 cm À1 represent C¼O stretching vibration of amide-I and bending vibration of NeH of amideeII, respectively, which confirms the consistence of helix structure of BSA [1,71,72] (Table 4). …”