Molecular Capture in Protein Nanotubes

Abstract

We describe molecular capturing properties of protein nanotubes with a controllable ligand binding affinity and size selectivity. These practical biocylinders were prepared using an alternating layer-by-layer (LbL) assembly of protein and oppositely charged poly(amino acid) into the nanoporous polycarbonate (PC) membrane (pore diameter, 400 nm), with subsequent dissolution of the template. The tube wall typically comprises six layers of poly-L-arginine (PLA) and human serum albumin (HSA) [(PLA/HSA)(3)]. Use of high molecular weight PLA (M(w) = ca. 70 000) yielded robust nanotubes, which are available as lyophilized powder. The (PLA/HSA)(3) nanotubes swelled considerably in water, although the outer diameter was almost unaltered. Uranyl ion, 3,3'-diethylthiacarbocyanine iodide, and zinc(II) protoporphyrin IX (ZnPP) were bound to the HSA component in the cylinder wall. Similar nanotubes comprising recombinant HSA mutant [rHSA(His)], which has a strong binding affinity for ZnPP, captured this ligand more tightly. Furthermore, addition of excess myristic acid released ZnPP from the tubes through a ligand replacement reaction. The hybrid nanotubes bearing a single avidin layer as an internal surface captured FITC-biotin efficiently. Biotin-labeled nanoparticles are also incorporated into the tubes when their particle size is sufficiently small to enter the pores. Subsequent TEM observation revealed a line of loaded nanoparticles (100 nm) in the one-dimensional space interior.

Human serum albumin: From bench to bedside

“…SA is a multi-functional protein having several biotechnological and biopharmaceutical applications, including O 2 transport and delivery (Tsuchida et al, 2009), nanodelivery of drugs (Qu and Komatsu, 2010;Komatsu et al, 2011aKomatsu et al, , 2011b, and fusion of peptides (Furukawa et al, 2011). Moreover, HSA appears to play a role in the development of implantable biomaterials, surgical adhesives, and surgical sealants due to its ability to coagulate (Subramanian et al, 2004;Spotnitz and Burks, 2008).…”

“…The nanotubes were prepared using an alternating layer-by-layer assembly of HSA and oppositely charged poly-L-Arg into a nanoporous polycarbonate membrane. The subsequent dissolution of the polycarbonate template yielded (poly-L-Arg/HSA) cylinders (Qu and Komatsu, 2010;Komatsu et al, 2011ab). Although the secondary structure of a-helices in HSA is slightly affected during the adsorption process and the random coils connecting a-helices are strongly altered, HSA retains functional properties .…”

Proteomic strategies and challenges in tumor metastasis research

“…New advances in mass spectrometry (MS) and protein microarray technology have reduced the threshold for protein detection to sub-nanogram levels [30]. Several strategies have also been developed for the depletion of highly abundant proteins and for enriching lowconcentration proteins, including different immunoaffinity Clin Exp Metastasis (2010) 27:441-451 443 [25,32,[37][38][39][40][41]. One important drawback of these methods is that several low abundance proteins or peptides, which are complexed to blood carrier proteins, such as albumin, are lost [33].…”

Effects of geometrical confinement in membrane pores on enzyme-based layer-by-layer assemblies

“…Therefore, different architectures such as protein planar films and coated microparticles, hollow capsules, coated membranes and nanotubes have been prepared. While most of the LbL research has been performed on planar or spherical surfaces, some groups also investigated deposition in membranes with cylindrical pores [20][21][22][23][24][25][26][27][28][29][30].…”