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Characterization of the size distribution and carbon components in particulates has become important for identifying the particulates in the atmosphere. The size distribution and carbon components of atmospheric particulate matter from motor vehicles in different regions were analyzed by using Micro-orifice uniform deposition impactors (MOUDI) and the organic carbon/elemental carbon (OC/EC) analyzer. With increasing particle size, the mass concentration of raw diesel/gasoline decreases. The highest mass concentration of particles collected near the chimney of an engine laboratory was observed for particle sizes ranging from 0.32-0.56 μm, while particles with sizes from 1.0-1.8 μm in the basement garage showed the most mass fractions. The OC1, OC2, and OC3 were the major parts of the OC contents in raw diesel particles. The EC2 was the main part of EC. The atmospheric particles collected in typical regions contained more OC3 and OC4. EC1 was the main part of EC in particles collected from the basement garage. The OC/EC ratios of raw diesel particles ranged from 0.92 to 2.50. The OC/EC ratios of particles collected near the chimney of an engine laboratory ranged from 1.40 to 2.53 and that of particles collected in the basement garage ranged from 2.36 to 4.82. Moreover, the OC/EC ratios in particles collected in the basement garage normally exceeded 2.0 and reached 4.82 at the largest size, which implies that many secondary particles were generated in the basement garage. The above-mentioned characteristics provide references that are beneficial for the identification of particulates in the atmosphere originating from motor vehicles.

Porphyrin is a kind of photosensitizer for photodynamic therapy of cancer. Many porphyrin derivatives have been used in clinical treatment. Human Serum Albumin (HSA) is the carrier of drug transportation. Therefore, investigation on the interaction of porphyrin with HSA is very important to understand the pharmacokinetic of the porphyrin. In this paper, a new water-soluble carboxyl porphyrins, meso-tetrakis(carboxyl) zinc(Ⅱ) porphyrin (2-Zn), was synthesized and characterized. Its interaction with human serum albumin (HSA)was investigated by UV-Vis absorption spectra, fluorescence spectra, circular dichroism (CD) spectra and molecular modeling. The results indicated that the fluorescence quenching of HSA by 2-Zn was a static process with the quenching constants are 1.96×104 L·mol-1 (298 K) and 1.37×104 L·mol-1 (310 K) and the binding constants were calculated to be 1.93×104 L·mol-1 (298 K) and 1.50×104 L·mol-1 (310 K). According to the Van’t Hoff equation, the thermodynamic parameters were characterized by negative enthalpy (ΔH=-16.132 kJ·mol-1) and positive entropy (ΔS=27.905 J·mol-1·K-1), which indicated that 2-Zn binds with HSA mainly via electrostatic interaction along with the hydrogen bonding and hydrophobic interaction. Site marker competitive binding experiment confirmed that 2-Zn mainly binds at site Ⅱ. The distance between HSA and the receptor (2-Zn) and the efficiency energy transfer were obtained to be 4.01 nm and 0.163 respectively, based on the Forster theory on resonance energy transfer. Synchronous fluorescence, absorption and CD spectroscopy showed that the interaction of HSA with 2-Zn induced a conformational change of protein, and the amount of α-helical structures were decrease. Furthermore, the binding details between 2-Zn and HSA were further studied with the molecular docking, which was in good agreement with the site marker competitive binding experiments and thermodynamic parameters.