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Investigation of proteins in their native state is the core of proteomics towards better understanding of their structures and functions. Surface-enhanced Raman spectroscopy (SERS) has shown its unique advantages in protein characterization with fingerprint information and high sensitivity, which makes it a promising tool for proteomics. It is still challenging to obtain SERS spectra of proteins in the native state and evaluate the native degree. Here, we constructed 3D physiological hotspots for a label-free dynamic SERS characterization of a native protein with iodide-modified 140 nm Au nanoparticles. We further introduced the correlation coefficient to quantitatively evaluate the variation of the native degree, whose quantitative nature allows us to explicitly investigate the Hofmeister effect on the protein structure. We realized the classification of a protein of SARS-CoV-2 variants in 15 min, which has not been achieved before. This study offers an effective tool for tracking the dynamic structure of proteins and biomedical research., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

We combined a microporous polymer backbone with an organic redox-active dopant to construct a reversible electrode system based on the conversion-(de)incorporation behaviour of the dopant. The correspondence between the reversible conversion-(de)incorporation mechanism of the dopant and the electrochemical performance of the designed electrode system was established by electrochemical quartz crystal microbalance and in situ Fourier transform infrared spectroscopy.

Leucine aminopeptidase (LAP), an important proteolytic enzyme, is closely associated with diverse physiological and pathological disorders such as liver injury and cancers. Hence, it is imperative to develop an effective method to detect LAP activity for early diagnosis of diseases. In this work, we report a novel SERS probe bis-s-s'-[(s)-2-amino-N-(3-thiophenyl)-Leu]. (b-(s)-ANT-Leu) with an l-leucine amide group, which can specially respond to LAP, to assay the LAP activity according to the SERS spectral changes between the probe molecule and its corresponding hydrolysis product resulting from the catalysis of LAP. This SERS approach features high selectivity on account of the specificity of the reaction combined with the instinctive fingerprinting ability of SERS and shows a good linear relationship in a wide range from 0.2 to 100 mU mL -1 with a detection limit as low as 0.16 mU mL -1 . In addition, the SERS-based strategy can be competent for LAP activity detection in clinical patient serum samples and LAP inhibitor evaluation, demonstrating its great potential in the pathological analysis for diseases involving LAP and the screening of LAP inhibitors.