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 700
Alexa Fluor™ 700 (AF700, Alexa 700) has an excitation peak at 702 nm and an emission peak at 723 nm, and is spectrally similar to iFluor® 680 (ATT Bioquest) and iFluor® 700 (ATT Bioquest). Alexa 700 is commonly used in Flow Cytometry and is similar in size, brightness and application to iFluor® 700 and Vio® R720.