title: Rapid identification of amino acid types in proteins using phase modulated 2D HN(CACB) and 2D HN(COCACB).
abstract: We present a simple approach to rapidly identify amino acid types in proteins from a 2D spectrum. The method is based on the fact that (13)C(β) chemical shifts of different amino acid types fall in distinct spectral regions. By evolving the (13)C chemical shifts in the conventional HNCACB or HN(CO)CACB type experiment for a single specified delay period, the phase of the cross peaks of different amino acid residues are modulated depending on their (13)C(β) shift values. Following this specified evolution period, the 2D HN projections of these experiments are acquired. The (13)C evolution period can be chosen such that all residues belonging to a given set of amino acid types have the same phase pattern (positive or negative) facilitating their identification. This approach does not require the preparation of any additional samples, involves the analysis of 2D [(15)N-(1)H] HSQC-type spectra obtained from the routinely used triple resonance experiments with minor modifications, and is applicable to deuterated proteins. The method will be useful for quick assignment of signals that shift during ligand binding or in combination with selective labeling/unlabeling approaches for identification of amino acid types to aid the sequential assignment process.
authors.affiliation: IISc Mathematics Initiative, Indian Institute of Science, Bangalore 560012, India; NMR Research Centre, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Abhinav
authors.initials: A
authors.lastname: Dubey
authors.affiliation: NMR Research Centre, Indian Institute of Science, Bangalore 560012, India; Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Somnath
authors.initials: S
authors.lastname: Mondal
authors.affiliation: NMR Research Centre, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Kousik
authors.initials: K
authors.lastname: Chandra
authors.affiliation: NMR Research Centre, Indian Institute of Science, Bangalore 560012, India. Electronic address: hsatreya@sif.iisc.ernet.in.
authors.forename: Hanudatta S
authors.initials: HS
authors.lastname: Atreya
mesh_terms: D000465:Algorithms; D000596:Amino Acids / Q000032:analysis* / Q000737:chemistry; D066241:Carbon-13 Magnetic Resonance Spectroscopy / Q000379:methods*; D010363:Pattern Recognition, Automated / Q000379:methods*; D011506:Proteins / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D020539:Sequence Analysis, Protein / Q000379:methods*; D012815:Signal Processing, Computer-Assisted
chemical_list: D000596:Amino Acids; D011506:Proteins
keywords: Amino acid-type assignments; Protein structure; Sequential assignments