Biomaterial Database

Urea denaturation of staphylococcal nuclease monitored by Fourier transform infrared spectroscopy. 1998

N B From, and B E Bowler

Department of Chemistry, University of Denver, Colorado 80208-2436, USA.

Fourier transform infrared (FTIR) amide I spectroscopy has not been widely used as a method to study protein folding. Some thorough studies of thermal unfolding have been carried out; however, protein unfolding in the presence of the widely used denaturants guanidine hydrochloride and urea has only recently been reported. Guanidine hydrochloride and urea both absorb strongly in the amide I region, as does H2O. Here, we have used deuterated 13C-urea as the chemical denaturant and monitored the unfolding transition with deuterium-exchanged staphylococcal nuclease (SNase) in D2O. These conditions circumvent all subtraction difficulties as the absorption bands of D2O and denaturant are shifted out of the amide I' region [Fabian, H., and Manstch, H. H. (1995) Biochemistry 34, 13651-13655]. A very reproducible unfolding transition is obtained for SNase. 13C-Urea-induced unfolding of SNase was found not only to be comparable to previous FTIR thermal unfolding data but also to have a denatured-state spectrum similar to those of other thermally denatured proteins. The unfolding is approximately two-state. The infrared spectra in the denatured state show evidence of some residual beta-sheet structure as well as other band components not attributable to random structure.

UI	MeSH Term	Description	Entries
D008836	Micrococcal Nuclease	An enzyme that catalyzes the endonucleolytic cleavage to 3'-phosphomononucleotide and 3'-phospholigonucleotide end-products. It can cause hydrolysis of double- or single-stranded DNA or RNA. (From Enzyme Nomenclature, 1992) EC 3.1.31.1.	Staphylococcal Nuclease,TNase,Thermonuclease,Thermostable Nuclease,Nuclease, Micrococcal,Nuclease, Staphylococcal,Nuclease, Thermostable
D011489	Protein Denaturation	Disruption of the non-covalent bonds and/or disulfide bonds responsible for maintaining the three-dimensional shape and activity of the native protein.	Denaturation, Protein,Denaturations, Protein,Protein Denaturations
D002942	Circular Dichroism	A change from planar to elliptic polarization when an initially plane-polarized light wave traverses an optically active medium. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Circular Dichroism, Vibrational,Dichroism, Circular,Vibrational Circular Dichroism
D014508	Urea	A compound formed in the liver from ammonia produced by the deamination of amino acids. It is the principal end product of protein catabolism and constitutes about one half of the total urinary solids.	Basodexan,Carbamide,Carmol
D014867	Water	A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Hydrogen Oxide
D017433	Protein Structure, Secondary	The level of protein structure in which regular hydrogen-bond interactions within contiguous stretches of polypeptide chain give rise to ALPHA-HELICES; BETA-STRANDS (which align to form BETA-SHEETS), or other types of coils. This is the first folding level of protein conformation.	Secondary Protein Structure,Protein Structures, Secondary,Secondary Protein Structures,Structure, Secondary Protein,Structures, Secondary Protein
D017510	Protein Folding	Processes involved in the formation of TERTIARY PROTEIN STRUCTURE.	Protein Folding, Globular,Folding, Globular Protein,Folding, Protein,Foldings, Globular Protein,Foldings, Protein,Globular Protein Folding,Globular Protein Foldings,Protein Foldings,Protein Foldings, Globular
D017550	Spectroscopy, Fourier Transform Infrared	A spectroscopic technique in which a range of wavelengths is presented simultaneously with an interferometer and the spectrum is mathematically derived from the pattern thus obtained.	FTIR,Fourier Transform Infrared Spectroscopy,Spectroscopy, Infrared, Fourier Transform
D017666	Deuterium Oxide	The isotopic compound of hydrogen of mass 2 (deuterium) with oxygen. (From Grant & Hackh's Chemical Dictionary, 5th ed) It is used to study mechanisms and rates of chemical or nuclear reactions, as well as biological processes.	Heavy Water,Oxide, Deuterium,Water, Heavy