Relaxation-assisted two-dimensional infrared (RA 2DIR) method: accessing distances over 10 A and measuring bond connectivity patterns.

摘要: Development of new approaches for measuring three-dimensional structures and dynamics structural changes is important a number natural sciences, including biology, where it can lead to understanding the physical bases molecular recognition catalysis. A two-dimensional infrared (2DIR) spectroscopy method permits pairwise interactions among vibrational modes in molecules providing scale ruler delivering constraints, such as distances between modes, angles their transition dipoles, energy-transfer rates them. While there large variety systems that have recently been interrogated using 2DIR, questions remain how measure features larger molecules. The challenges working with molecules, proteins, include very congested spectra, small range accessible by 2DIR method, sensitivity issues. This Account describes efforts our laboratory overcome some these challenges. First, we discuss dual-frequency approach, which provides highest selectivity particular pair reporters sensitivity. Second, describe steps developing labels, novel C identical withN C-D stretching frequencies water transparency region, well fingerprint region. schemes suitable labeling amino acids are discussed. Next, relaxation-assisted (RA 2DIR) developed laboratory. uses relaxation energy transport thermalization process on scale, generate stronger cross-peaks. An 18-fold cross-peak amplification was observed separated about 11 RA amplifications expected modes. Large provided enhances longer measurements. In addition generating cross-peaks, correlation time intermode distance demonstrated. measurements mode-connectivity patterns much similar those available total (TOCSY) heteronuclear multiple-bond (HMBC) methods 2D nuclear magnetic resonance (NMR) spectroscopy. It hope that, proper calibration, will permit speedy assessments bond connectivity reach level an analytical method.