The Flow Cytometry Absolute Count Standard™ is a precisely counted population of microspheres for estimating counts of unlabeled cells via flow cytometry. The microspheres are ~7-9µm in diameter and supplied at ~1e+6 beads/mL. Beads are internally labeled with multiple fluorophores for excitation with common lasers (e.g. 488nm, 633nm) and discrimination from the cell population. By evaluating the ratio of microspheres to cells, the volumetric number of cells may be determined. For more Flow Cytometry Resources, visit the Bangs Flow Blog.

转染技术新宠-Polysciences阳离子聚合物基因转染技术 其优点：适用宿主广泛，操作简便，细胞毒性小，转染率高。其中聚乙烯亚胺（PEI）的转染性能最好。聚乙烯亚胺是一种具有较高的阳离子电荷密度的有机大分子，每相隔两个碳原子，就是第三个原子都是质子化的氨基氮原子，使得聚合物网络在任何PH下都能充当有效的“质子海绵”体。这种聚阳离子能将各种报告基因转入各种种属细胞，其效果好于脂质聚酰胺，而且细胞毒性低。大量实验证明，PEI是非常有希望的基因治疗载体。目前在设计更复杂的基因载体时，PEI经常做为核心组成成分。