About Activin RIIB
Activins are dimeric growth and differentiation factors which belong to the transforming growth factor-beta (TGF-beta) superfamily of structurally related signaling proteins. Activins signal through a heteromeric complex of receptor serine kinases which include at least two type I (I and IB) and two type II (II and IIB) receptors. These receptors are all transmembrane proteins, composed of a ligand-binding extracellular domain with cysteine-rich region, a transmembrane domain, and a cytoplasmic domain with predicted serine/threonine specificity. Type I receptors are essential for signaling; and type II receptors are required for binding ligands and for expression of type I receptors. Type I and II receptors form a stable complex after ligand binding, resulting in phosphorylation of type I receptors by type II receptors. Type II receptors are considered to be constitutively active kinases. This gene encodes activin A type IIB receptor, which displays a 3- to 4-fold higher affinity for the ligand than activin A type II receptor. [provided by RefSeq, Jul 2008]

About Alexa Fluor 488
Alexa Fluor™ 488 (AF488, Alexa 488) has an excitation peak at 488 nm and an emission peak at 496 nm, and is considered a high-performance alternative to FITC. Alexa 488 is one of the most popular Alexa Fluor™ dyes and is widely used in Fluorescence Microscopy, flow cytometry, and for staining low expression markers. It is bright, highly photostable, resistant to pH changes, and less susceptible to photobleaching. Alexa 488 and is similar in size, brightness and application to DyLight™ 488, iFluor® 488 and CF®488A.