title: Four pulse recoupling.
abstract: The paper describes a family of novel recoupling pulse sequences in magic angle spinning (MAS) solid state NMR, called four pulse recoupling. These pulse sequences can be employed for both homonuclear and heteronuclear recoupling experiments and are robust to dispersion in chemical shifts and rf-inhomogeneity. The homonuclear pulse sequence consists of a building block π20°3π2ϕ°π2180°+ϕ°3π2180°where ϕ=πnϕ°=180°n, and n is number of blocks in a two rotor period. The heteronuclear recoupling pulse sequence consists of a building block [Formula: see text] and [Formula: see text] on channel I and S, where ϕ1=3π2n,ϕ2=π2n and n is number of blocks in a two rotor period. The recoupling pulse sequences mix the y magnetization. We show that four pulse recoupling is more broadband compared to three pulse recoupling [1]. Experimental quantification of this method is shown for13Cα-13CO, homonuclear recoupling in a sample of Glycine and15N-13Cα, heteronuclear recoupling in Alanine. Application of this method is demonstrated on a sample of tripeptide N-formyl-[U-13C,15N]-Met-Leu-Phe-OH (MLF).
authors.affiliation: Department of Electrical Engineering, IIT Bombay, Powai, 400076, India. Electronic address: navinkhaneja@gmail.com.
authors.forename: Navin
authors.initials: N
authors.lastname: Khaneja
authors.affiliation: Department of Biosciences and Bioengineering, IIT Bombay, Powai, 400076, India.
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Kumar
keywords: Broadband recoupling; Hartmann Hahn match; MAS; Recoupling; rf-inhomogeneity