@article{guo_he_2007, title={A binary matrix for background suppression in MALDI-MS of small molecules}, volume={387}, ISSN={["1618-2642"]}, DOI={10.1007/s00216-006-1100-3}, abstractNote={Application of matrix-assisted laser-desorption ionization mass spectrometry (MALDI-MS) to small-molecule detection is often limited, because of high matrix background signals in the low-mass region. We report here an approach in which a mixture of two conventional MALDI matrices with different proton affinity was used to suppress the formation of matrix clusters and fragments. Specifically, when acidic alpha-cyano-4-hydroxycinnamic acid (CHCA) and basic 9-aminoacridine (9-AA) were used as the binary matrix, fewer background matrix peaks were observed in both positive and negative-mode detection of small molecules. In addition, the presence of CHCA substantially reduced the laser fluence needed for analyte desorption and ionization; thus better signal-to-background ratios were observed for negatively charged inositol phosphates in complex plant extracts.}, number={5}, journal={ANALYTICAL AND BIOANALYTICAL CHEMISTRY}, author={Guo, Zhong and He, Lin}, year={2007}, month={Mar}, pages={1939–1944} }
 @article{liu_guo_he_2007, title={Mass spectrometry imaging of small molecules using desorption/ionization on silicon}, volume={79}, ISSN={["1520-6882"]}, DOI={10.1021/ac0611465}, abstractNote={Development of novel tools to image spatial distribution of small molecules in biological samples is essential in disease diagnosis and biomarker discovery. To simplify sample preparation and reduce background noise in the low-mass region, we describe here the use of a matrix-free mass spectrometric imaging method, i.e., desorption/ionization on silicon (DIOS), for biological surface analysis. The imaging parameters, such as the laser beam diameter and the translation stage movement, were studied and optimized to improve imaging performance. The use of DIOS imaging to map small molecules on mouse liver tissues was demonstrated. In addition, phosphatidylcholine (PC) and propidium iodide (PI) were used as the cell membrane and nucleus markers, respectively, to "visualize" the presence of HEK 293 cells. The reconstructed ion maps of PC and PI were compared with the optical images collected from the same sample using bright-field and fluorescence microscopy. A good correlation of the spatial distribution of cells confirmed the validity of this DIOS imaging approach.}, number={10}, journal={ANALYTICAL CHEMISTRY}, author={Liu, Qiang and Guo, Zhong and He, Lin}, year={2007}, month={May}, pages={3535–3541} }
 @misc{guo_ganawi_liu_he_2006, title={Nanomaterials in mass spectrometry ionization and prospects for biological application}, volume={384}, ISSN={["1618-2650"]}, DOI={10.1007/s00216-005-0125-3}, abstractNote={The rapid development of nanotechnology has revolutionized scientific developments in recent decades. Mass spectrometry (MS) measurements are no exception and have benefited greatly from integration of nanomaterials in every step of analysis. This brief review summarizes recent developments in the field with the focus on the use of nanomaterials as alternative media to facilitate analyte ionization in laser-desorption ionization-mass spectrometry (LDI-MS) and secondary ion mass spectrometry (SIMS). The biological applications of both techniques are also detailed. The use of nanomaterials in other aspects of MS analysis, for example in sample clean-up and indirect analyte quantification, is briefly discussed.}, number={3}, journal={ANALYTICAL AND BIOANALYTICAL CHEMISTRY}, author={Guo, Z and Ganawi, AAA and Liu, Q and He, L}, year={2006}, month={Feb}, pages={584–592} }