Secondary Structure Analysis of Proteins Embedded in Spherical Polyelectrolyte Brushes by FT-IR Spectroscopy

Abstract

The adsorption of bovine serum albumin (BSA), bovine beta-lactoglobulin, and bovine pancreatic ribonuclease A onto spherical polyelectrolyte brushes (SPB) is reported. The SPB consist of narrowly distributed poly(styrene) core particles (diameter approximately 100 nm) onto which linear chains of anionic polyelectrolytes are grafted. The polyelectrolyte shell consists of either the weak polyelectrolyte poly(acrylic acid) or the strong polyacid poly(styrenesulfonate). The SPB particles are dispersed in H(2)O at room temperature. The secondary structure of the proteins was investigated by Fourier transform infrared spectroscopy in transmission mode before and during adsorption to these colloidal brushes. The alpha-helix and beta-sheet content of the proteins was nearly fully retained in the adsorbed state for all systems. Only in the case of BSA interacting with poly(styrenesulfonic) brushes could a slight loss of alpha-helix structure be observed. As the interaction of SPB and proteins can be controlled by the ionic strength in the buffer, additional experiments were performed to release the adsorbed protein. The amount of released protein was quantified and was found to be strongly dependent on the kind of protein and brush used. The secondary structure of the released proteins could be analyzed as well. An almost full preservation of secondary structure was found. This demonstrates that SPB are well-suited to immobilize proteins. The SPB can be charged and decharged under retention of the secondary structure of the biomolecules.

Angiogenic properties of natural rubber latex biomembranes and the serum fraction of Hevea brasiliensis

“…The features in the spectra are probably associated with the secondary struc- ture of proteins, as identified by the amide bands (amide I -1620-1700 cm-1) and amide II -1520-1580 cm-1) [32,33]. This region is represented between dashed lines in Figure 7.…”

Supramolecular Structures Generated by Spherical Polyelectrolyte Brushes and their Application in Catalysis

“…[57] Raising the ionic strength leads to a release of most of the adsorbed protein. [54,58] Hence, the SPB can be viewed upon as ''nanoreactors'' that can be charged or decharged with the catalyst. [59] Moreover, a recent study using BSA could demonstrate that this release proceeds in steps if the salt concentration is raised stepwise.…”

“…[55] (2) Previous studies by FT-IR have shown that the secondary structure of the adsorbed BSA, b-lactoglobulin and of ribonuclease A is nearly undisturbed. [58,62] Moreover, the activity of adsorbed enzymes as glucoamylase is largely preserved. [33] The same conclusion was drawn from a study of the fluorescence activity of the fluorescent protein mEosFP.…”

Temperature‐Induced Unfolding of Ribonuclease A Embedded in Spherical Polyelectrolyte Brushes

“…[14][15][16][17][18][19] Recently, we presented a novel approach for the immobilization of proteins: Colloidal particles bearing densely grafted polyelectrolyte brushes on their surface provide a new class of carrier particles for adsorbed proteins with unique properties. [20][21][22][23][24] The spherical polyelectrolyte brushes (SPB) shown in Figure 1 consisting of a poly(styrene) core and poly(styrene sulfonate) shell provide high adsorption degrees as long as the ionic strength is kept low. [20] This effect refers to the so-called osmotic limit where the polyelectrolyte chains are strongly stretched due to the osmotic pressure of the counterions confined within the brush.…”