Single-protein spin resonance spectroscopy under ambient conditions

Abstract

Magnetic resonance is essential in revealing the structure and dynamics of biomolecules. However, measuring the magnetic resonance spectrum of single biomolecules has remained an elusive goal. We demonstrate the detection of the electron spin resonance signal from a single spin-labeled protein under ambient conditions. As a sensor, we use a single nitrogen vacancy center in bulk diamond in close proximity to the protein. We measure the orientation of the spin label at the protein and detect the impact of protein motion on the spin label dynamics. In addition, we coherently drive the spin at the protein, which is a prerequisite for studies involving polarization of nuclear spins of the protein or detailed structure analysis of the protein itself.

Unambiguous nuclear spin detection using an engineered quantum sensing sequence

“…The amplitude of spurious high-order resonance signals are also relatively smaller using YY8 pulse sequence even when the initial phase is not perfect. These advantageous features of YY8 pulse sequence allows for the efficient unambiguous identification of nuclear spins, in particular it implies that YY8 pulse sequence can unambiguously identify the signal from 1 H, while avoiding the possible confusion with the 4 th harmonic signal of 13 C with no extra experiment requirement as compared with the already widely used XY8 pulse sequence.…”

“…As an example, we consider the detection of 13 C nucleus in bulk diamond. The hyperfine interaction between the NV center spin and the nuclear spin is described by…”

“…Using single nitrogen-vacancy spin sensor in diamond, we demonstrate the simultaneous suppression of both the 2 nd and the 4 th order spurious resonance e.g. from the surrounding 13 C nuclei in diamond in proton sensing. We also observe the effect of the initial phase φ i in the XY8 family pulse sequences π [35].…”

“…The achievement of this goal may have significant impact on structural biology and medical imaging and may also provide a new tool for the investigation of nuclear spin dynamics in non-trivial quantum biological processes [2,3]. Recently, research has made impressive progress in single nuclear spin detection using various physical platforms [4][5][6][7][8], particularly in the highly challenging task of detecting single spins in external molecules [9][10][11][12][13][14]. Among those physical platforms, a sensor based on individual negatively charged nitrogen-vacancy (NV) centers in diamond [15,16] has demonstrated appealing prospects for applications in biology and medicine, due to its biocompatibility, nano-scale size and long coherence times under ambient conditions [17,18].…”

“…Among those physical platforms, a sensor based on individual negatively charged nitrogen-vacancy (NV) centers in diamond [15,16] has demonstrated appealing prospects for applications in biology and medicine, due to its biocompatibility, nano-scale size and long coherence times under ambient conditions [17,18]. NV centers, shallowly implanted to within a few nanometers below the diamond surface, enable strong coupling between NV sensors and target nuclei, thereby promoting the detection sensitivity from a relative large ensemble of nuclei [9,10] to single nuclear spin sensitivity in small clusters of nuclear spins [11][12][13][14]. Besides the interest in single molecule magnetic resonance spectroscopy and imaging, single nuclear spin addressing also has an important role to play in the precise coherent control of nuclear spin qubits, where it may facilitate the realisation of quantum memories with long coherence times and nuclear spin based quantum information processors [19][20][21][22].…”