title: Protein nanotubes comprised of an alternate layer-by-layer assembly using a polycation as an electrostatic glue.
abstract: We present the synthesis and structure of various protein nanotubes comprised of an alternate layer-by-layer (LbL) assembly using a polycation as an electrostatic glue. The nanotubes were fabricated by sequential LbL depositions of positively charged polycations and negatively charged proteins into a porous polycarbonate (PC) membrane, followed by release of the cylindrical core by quick dissolution of the template with CH(2)Cl(2). This procedure provides a variety of protein nanotubes without interlayer cross-linking. The three-cycle depositions of poly-L-arginine (PLA) and human serum albumin (HSA, M(w)=66.5 kDa) into the porous PC template (pore diameter, D(p)=400 nm) yielded well-defined (PLA/HSA)(3) nanotubes with an outer diameter of 419+/-29 nm and a wall thickness of 46+/-8 nm, revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. The outer diameter of the tubules can be controlled by the pore size of the template (200-800 nm), whereas the wall thickness is always constant, independent of the D(p) value. The (PEI/HSA)(3) (PEI: polyethylenimine) nanotubes showed a slightly thin wall of 39+/-5 nm. CD spectra of the multilayered (PEI/HSA)(n) film on a flat quartz plate suggested that the secondary structure of HSA between the polycations was almost the same as that in aqueous solution. The three-cycle LbL depositions of PLA and ferritin (M(w)=460 kDa) or myoglobin (Mb, M(w)=1.7 kDa) into the porous PC membrane also gave cylindrical hollow structures. The wall thickness of the (PLA/ferritin)(3) and (PLA/Mb)(3) nanotubes were 55+/-5 nm and 31+/-4 nm; it depends on the globular size of the protein (ferritin>HSA>Mb). The individual ferritin molecule was clearly seen in the tubular walls by SEM and TEM measurements.
authors.affiliation: Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo, Japan.
authors.forename: Xue
authors.initials: X
authors.lastname: Qu
authors.forename: Gang
authors.initials: G
authors.lastname: Lu
authors.forename: Eishun
authors.initials: E
authors.lastname: Tsuchida
authors.forename: Teruyuki
authors.initials: T
authors.lastname: Komatsu
mesh_terms: D000269:Adhesives / Q000737:chemistry*; D000818:Animals; D005293:Ferritins / Q000737:chemistry*; D006736:Horses; D006801:Humans; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D009211:Myoglobin / Q000737:chemistry*; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure; D011073:Polyamines / Q000737:chemistry*; D000071228:Polyelectrolytes; D012709:Serum Albumin / Q000737:chemistry*; D055672:Static Electricity
chemical_list: D000269:Adhesives; D005293:Ferritins; D009211:Myoglobin; D011073:Polyamines; D000071228:Polyelectrolytes; D012709:Serum Albumin