Label-Free Surface-Enhanced Raman Spectroscopic Analysis of Proteins: Advances and Applications.

Surface-enhanced Raman spectroscopy (SERS) is powerful for structural characterization of biomolecules under physiological condition. Owing to its high sensitivity and selectivity, SERS is useful for probing intrinsic structural information of proteins and is attracting increasing attention in biophysics, bioanalytical chemistry, and biomedicine. This review starts with a brief introduction of SERS theories and SERS methodology of protein structural characterization. SERS-active materials, related synthetic approaches, and strategies for protein-material assemblies are outlined and discussed, followed by detailed discussion of SERS spectroscopy of proteins with and without cofactors. Recent applications and advances of protein SERS in biomarker detection, cell analysis, and pathogen discrimination are then highlighted, and the spectral reproducibility and limitations are critically discussed. The review ends with a conclusion and a discussion of current challenges and perspectives of promising directions.

Release of soluble ions and heavy metal during fly ash washing by deionized water and sodium carbonate solution.

Two municipal solid waste incineration fly ashes were selected for washing by deionized water and Na2CO3 solution for comparison. Results showed that the benefits of washing were two folds: (1) Washing was able to reduce the contents of Cl- and SO42- while increased the contents of CaO, SiO2, Al2O3 etc.; (2) Washing by Na2CO3 solution showed increased stability of heavy metals (Cr, Ni, Cd, Cu, Zn and Pb) and fly ash was safe for later reuse. Release of Cl- was high at more than 90% regardless of washing solution. SO42- and Ca2+ removal was highly dependent on the dissolution and precipitation equilibriums. Na2CO3 washing promoted the formation of CaCO3. Thus SO42- was washed off instead of precipitating as CaSO4 and retained in fly ash solid. SO42- removal was raised to more than 80% by Na2CO3 washing as compared with about 30% by deionized water. At the same time, Ca removal by Na2CO3 dropped to 1-2%. In addition, the basicity of fly ash was important as high basicity helped SO42- removal. Overall, washing by Na2CO3 appears to be a promising option for fly ash treatment.