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.

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Body mass index is a practical and valuable measurement for the prediction of the perioperative outcome of laparoscopic colorectal surgery. Higher BMI is associated with worse perioperative outcome. More accurate conclusions, with more precise cutoff values, can be achieved by future well-designed prospective investigations.