Synthesis of a Möbius carbon nanobelt

New technologies for the creation of topological carbon nanostructures have significantly advanced synthetic organic chemistry and materials science. While simple molecular nanocarbons with a belt topology have been constructed recently, analogous carbon nanobelts with a twist, i.e., Möbius carbon nanobelts (MCNBs), have not yet been synthesized due to their high intrinsic strain. Herein, we report the synthesis, isolation, and characterization of a MCNB. Calculations of strain energies suggested that large MCNBs are synthetically accessible. Designing a macrocyclic precursor with an odd number of repeat units led to a successful rational synthetic route via Z-selective Wittig reactions and nickel-mediated intramolecular homocoupling reactions, which yielded (25,25)MCNB over 14 steps. NMR and theoretical calculations revealed that the twist moiety of the Möbius band moves quickly around the MCNB molecule in solution. The topological chirality originating from the Möbius structure was confirmed experimentally using chiral HPLC separation and CD spectroscopy.

Download Full-text

Isolation and characterization of a polymerized prion protein

Biochemical Journal ◽

10.1042/bj3640081 ◽

2002 ◽

Vol 364 (1) ◽

pp. 81-87 ◽

Cited By ~ 24

Author(s):

Bao-Yuan LU ◽

Jui-Yoa CHANG

Keyword(s):

Prion Protein ◽

Cd Spectroscopy ◽

Reversed Phase ◽

Size Exclusion ◽

Proteinase K ◽

Guanidinium Chloride ◽

Isolation And Characterization ◽

Size Exclusion Hplc ◽

Β Sheet

A polymerized form of recombinant mouse prion protein (mPrP) domain 23–231 [mPrP-(23–231)], designated mPrP-z, was generated at acidic pH (pH 2–5) in the presence of selected concentrations of denaturant (2M guanidinium chloride or 5M urea). This isoform of mPrP is stable in acidic solution after removal of denaturant. It can be isolated and purified using reversed-phase HPLC or size-exclusion HPLC. mPrP-z bears structural properties that partially resemble those of scrapie prion. Unlike the native mPrP-(23–231) (mPrP-N), mPrP-z exhibits a high content of β-sheet structure, as shown by CD spectroscopy, and exists as an oligomer with an approximate molecular mass of 340000Da, as measured by light scattering. However, similarly to mPrP-N, mPrP-z contains the intact disulphide bond and is sensitive to digestion by proteinase K.

Download Full-text

Investigating Viruses During the Transformation of Molecular Biology: Part II

Annual Review of Virology ◽

10.1146/annurev-virology-021020-100558 ◽

2020 ◽

Vol 7 (1) ◽

pp. 15-36

Author(s):

Bernard Moss

Keyword(s):

Molecular Biology ◽

Messenger Rna ◽

New Technologies ◽

Helical Structure ◽

Early Years ◽

Expression Vectors ◽

Recombinant Vaccines ◽

Isolation And Characterization

My scientific career started at an extraordinary time, shortly after the discoveries of the helical structure of DNA, the central dogma of DNA to RNA to protein, and the genetic code. Part I of this series emphasizes my education and early studies highlighted by the isolation and characterization of numerous vaccinia virus enzymes, determination of the cap structure of messenger RNA, and development of poxviruses as gene expression vectors for use as recombinant vaccines. Here I describe a shift in my research focus to combine molecular biology and genetics for a comprehensive understanding of poxvirus biology. The dominant paradigm during the early years was to select a function, isolate the responsible proteins, and locate the corresponding gene, whereas later the common paradigm was to select a gene, make a mutation, and determine the altered function. Motivations, behind-the-scenes insights, importance of new technologies, and the vital roles of trainees and coworkers are emphasized.

Download Full-text

Isolation and characterization of haemoporin, an abundant haemolymph protein from Aplysia californica

Biochemical Journal ◽

10.1042/bj20030726 ◽

2003 ◽

Vol 375 (3) ◽

pp. 681-688 ◽

Cited By ~ 1

Author(s):

Elmar JAENICKE ◽

Patrick J. WALSH ◽

Heinz DECKER

Keyword(s):

Quaternary Structure ◽

Aplysia Californica ◽

Circulatory System ◽

Sedimentation Coefficient ◽

Helical Structure ◽

Cd Spectroscopy ◽

Macromolecular Complex ◽

Marine Gastropod ◽

Isolation And Characterization

In the present study, we show the isolation and characterization of the protein haemoporin, which constitutes the second most abundant protein fraction in the haemolymph of the marine gastropod Aplysia californica. Although Aplysia is commonly used to investigate the molecular basis of learning, not much is known about the proteins in its haemolymph, which is in contact with the neurons owing to the open circulatory system of molluscs. In the native state, haemoporin is a macromolecular complex forming a cylinder with a central solvent-filled pore. The native complex most probably is a homopentamer made up from 70 kDa subunits with a molecular mass of 360 kDa and a sedimentation coefficient of 11.7 S. Prediction of the secondary structure by CD spectroscopy revealed that haemoporin contains 36% α-helices and 19% β-strands. An absorption band in the 300–400 nm region indicates that haemoporin probably contains a bound substance. Haemoporin also contains a below average amount of tryptophan as evident from absorption and fluorescence spectra. The specific absorption coefficient at 280 nm (a280 nm, 1 mg/ml) varies between 0.42 and 0.59 l·g−1·cm−1 depending on the method. The function of the protein is not yet known, but there are structural parallels between haemoporin and a pore protein reported previously in the haemolymph of another marine gastropod Megathura crenulata. The alanine-rich N-terminal sequence (AAVPEAAAEATAEAAPVSEF) is unique among protein sequences and indicates an α-helical structure. Whereas one side of the helix is hydrophobic and faces the interior of the protein, the other side contains a glutamic cluster, which may form the channel of the pore in the quaternary structure. Thus both proteins might belong to a new class of haemolymph proteins present in the haemolymph of marine gastropods.

Download Full-text

Applications of ultramicrotomy for materials characterization

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100147004 ◽

1993 ◽

Vol 51 ◽

pp. 232-233

Author(s):

R.T. Blackham ◽

J.J. Haugh ◽

C.W. Hughes ◽

M.G. Burke

Keyword(s):

Materials Science ◽

Microstructural Analysis ◽

Analytical Electron Microscopy ◽

Austenitic Stainless Steels ◽

Specimen Preparation ◽

Preparation Technique ◽

Thermally Induced ◽

Radiation Induced ◽

Characterization Of Materials

Essential to the characterization of materials using analytical electron microscopy (AEM) techniques is the specimen itself. Without suitable samples, detailed microstructural analysis is not possible. Ultramicrotomy, or diamond knife sectioning, is a well-known mechanical specimen preparation technique which has been gaining attention in the materials science area. Malis and co-workers and Glanvill have demonstrated the usefulness and applicability of this technique to the study of a wide variety of materials including Al alloys, composites, and semiconductors. Ultramicrotomed specimens have uniform thickness with relatively large electron-transparent areas which are suitable for AEM anaysis.Interface Analysis in Type 316 Austenitic Stainless Steel: STEM-EDS microanalysis of grain boundaries in austenitic stainless steels provides important information concerning the development of Cr-depleted zones which accompany M23C6 precipitation, and documentation of radiation induced segregation (RIS). Conventional methods of TEM sample preparation are suitable for the evaluation of thermally induced segregation, but neutron irradiated samples present a variety of problems in both the preparation and in the AEM analysis, in addition to the handling hazard.

Download Full-text