大气气溶胶粒子的热动力学过程主要源于多元物质的非理想混合, 其演化过程包括液-液相分离、吸湿-挥发、非平衡传质等。相关物理化学参数是理解气溶胶演化过程、分析演化动因、预测演化路径的基础, 而精确的单粒子测量是获取这些重要参数的关键。利用自主开发的气溶胶拉曼光镊系统, 实现了单颗粒气溶胶液滴无接触长时间捕获, 并通过改变气溶胶粒子所处环境的相对湿度, 模拟了实际大气中悬浮气溶胶液滴的吸湿-挥发热力学演化过程。通过测量单颗粒液滴粒子的腔共振拉曼光谱信号, 结合相应的物理模型精确测量了氯化钠、蔗糖和柠檬酸三种不同气溶胶液滴粒子在吸湿-挥发过程中的粒径、折射率、扩散系数、挥发通量等重要物化参数, 分析了有机/无机气溶胶液滴的吸湿-挥发特性对相对湿度变化的不同响应以及气溶胶液滴可能存在的玻璃态、胶态等相变行为, 为理解实际大气气溶胶吸湿-挥发过程提供了重要参考。

受衍射极限的限制，传统光学显微镜的分辨率只能达到入射光波长的一半。超分辨显微镜已有很多，但制作工艺复杂，适用样品有限，对成像条件要求苛刻，因此应用受到很多限制。研究表明，将直径为几微米至几十微米的透明电介质微球置于样品表面，能显著提高传统光学显微镜的分辨能力，在白光下即可实现超分辨成像，与其他类型显微镜结合使用时也能保持超分辨能力。这种新型透镜为纳米结构和生物样本的实时超分辨成像提供了一种简单、直接的方式。结合本课题组研究结果，介绍并总结了国内外微球透镜的研究进展。

Activating mutants in rat sarcoma (RAS) and B-rapid accelerated fibrosarcoma (BRAF) are found in at least a third of cases of human tumors and melanoma; hence, numerous therapeutic treatments target this pathway. In this letter, we study the adhesion force of RAS-coated beads with BRAF-coated beads, BRAF (A246P) mutant–coated beads, and GST-coated beads using optical tweezers. One full and two fractional RAS–BRAF specific binding modes are identified using the rupture force distribution. The koff (0) of the full binding mode in RAS–BRAF is 3.71×10-4/s and 1.16×10-4s-1 in RAS–BRAF (A246P), whereas the xb is around 3 \times 10-10 m in both groups.

We carry out in situ single-molecule measurements of the specific interaction between apolipoprotein A-I (apoA-I) and ATP binding cassette transporter A1 (ABCA1) on THP-1 cells. Single-molecule force spectroscopy shows that similar to normal apoA-I, the dysfunctional apoA-I from diabetes patients interacts with ABCA1 via two different binding sites on the cells. The strength of dysfunctional apoA-I binding to a high-capacity binding site is 26.5+(-)4.9 pN. The minor direct apoA-I/ABCA1 binding strength is 56.7+(-)4.1 pN. These results facilitate a pathological understanding of the mechanisms that underlie the specific interaction of apoA-I and ABCA1 at the single-molecule level.

We investigate the activation of living monocytic U937 cells induced by interleukin-6 (IL-6) at the single cell level. We employ home-built Raman tweezers to measure the Raman spectra of living U937 cells with and without IL-6 at the single cell level. Raman peaks of amide III, amide I, DNA backbone, as well as guanine and adenine in U937 cells, change at 1312, 1652, 1090, and 1576 cm ?1, respectively, shortly after IL-6 is added in the medium. The change is a dynamic temporal process. In the activation process of U937 cells induced by IL-6, the protein signals recover in 20 min, while the nucleic acid signals continue to increase for 20 min. The results reveal that the biochemical cascades of activation in signal transduction induced by IL-6 can be investigated in situ at the single cell level.

论述了一种与光镊结合的显微拉曼光谱即“光镊显微拉曼光谱”系统的构建方案。给出了利用该系统测得的活细胞(大白鼠血细胞,酵母细胞)的微区拉曼光谱,并将红外光镊束缚下的Ar+激光激发的血细胞的拉曼光谱,与用单一Ar+激光光镊束缚并同时激发的血细胞拉曼光谱,以及血细胞直接贴在基底上的拉曼光谱进行了分析对比。实验表明,前者比后两种实验方案的血细胞拉曼光谱信号有显著提高。分析了红外1064 nm光镊激光和可见514.5 nm Ar+激光对活细胞的损伤效应,发现高功率的红外激光对细胞的损伤作用远小于低功率的Ar+激光。并将该系统应用于碳纳米管材料分析,获得了单壁碳纳米管的拉曼光谱。

Accurate calibrations of stiffness and position are crucial to the quantitative measurement with optical tweezers. In this paper, we present a new calibration scheme for optical tweezers including stiffness and position calibrations. In our system, acousto-optic deflectors (AODs) are used as laser beam manipulating component. The AODs are controlled by a field programmable gate array (FPGA) connected to a computer using universal serial bus (USB) communication mode. Our results agree well with the present theory and other experimental results.