The mechanism of the colour shift of astaxanthin in alpha-crustacyanin as investigated by C-13 MAS NMR and specific isotope enrichment

By selective isotope enrichment of astaxanthin, MAS NMR and semi-empirical modelling, ligand-protein interactions associated with the red shift in alpha-crustacyanin, the major blue astaxanthin binding carotenoprotein complex from the carapace of the lobster Homarus gammarus, have been analysed. C-13 Magic Angle Spinning (MAS) NMR spectra were obtained after reconstitution with astaxanthins labelled in the centre of the molecule or at the two keto groups. The MAS data reveal electrostatic polarizations of the conjugated chain. In addition, solid state NMR results for pure unlabelled astaxanthin can be compared with natural abundance C-13 MAS data for canthaxanthin and beta-carotene, to address the effect of the ring functionalities on the electronic properties of the polyene chain. Quantum chemical calculations were performed to reconcile the MAS data with one of several simple and straightforward mechanisms for the colour shift. The results point towards a colour shift mechanism in which the astaxanthin may be doubly charged, possibly by a double protonation of the two ring keto groups.Bio-organic SynthesisSolid state NMR/Biophysical Organic Chemistr

Protein-chromophore interactions in α-crustacyanin, the major blue carotenoprotein from the carapace of the lobster, homarus gammarus a study by 13C magic angle spinning NMR

Bio-organic Synthesi

13C Magic Angle Spinning NMR Analysis and Quantum Chemical Modeling of the Bathochromic Shift of Astaxathin in a-Crustacyanin, the Blue Carotenoprotein Complex in the Carapace of the Lobster Homarus gammarus

Bio-organic Synthesi

Resonance Raman spectroscopy and quantum chemical modeling studies of protein-astaxanthin interactions in alpha-crustacyanin (major blue carotenoprotein complex in carapace of lobster, Homarus gammarus)

Solid state NMR/Biophysical Organic ChemistryBio-organic Synthesi

Carotenoid blues: Structural studies on carotenoproteins

Solid state NMR/Biophysical Organic Chemistr

Spectroscopic studies of molecular interactions in carotenoproteins

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN004257 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Design and self-assembly of simple coat proteins for artificial viruses

Viruses are among the simplest biological systems and are highly effective vehicles for the delivery of genetic material into susceptible host cells1. Artificial viruses can be used as model systems for providing insights into natural viruses and can be considered a testing ground for developing artificial life. Moreover, they are used in biomedical and biotechnological applications, such as targeted delivery of nucleic acids for gene therapy1, 2 and as scaffolds in material science3, 4, 5. In a natural setting, survival of viruses requires that a significant fraction of the replicated genomes be completely protected by coat proteins. Complete protection of the genome is ensured by a highly cooperative supramolecular process between the coat proteins and the nucleic acids, which is based on reversible, weak and allosteric interactions only6, 7, 8, 9. However, incorporating this type of supramolecular cooperativity into artificial viruses remains challenging10, 11, 12, 13, 14, 15. Here, we report a rational design for a self-assembling minimal viral coat protein based on simple polypeptide domains. Our coat protein features precise control over the cooperativity of its self-assembly with single DNA molecules to finally form rod-shaped virus-like particles. We confirm the validity of our design principles by showing that the kinetics of self-assembly of our virus-like particles follows a previous model developed for tobacco mosaic virus9. We show that our virus-like particles protect DNA against enzymatic degradation and transfect cells with considerable efficiency, making them promising delivery vehicles

Ex Post Problems in Buyer–Supplier Transactions: Effects of Transaction Characteristics, Social Embeddedness, and Contractual Governance

This paper focuses on ex post governance of inter-firm transactions. We develop and test hypotheses on the occurrence of ex post problems like delivery delays, inferior quality, and insufficient service in buyer–supplier transactions. Our hypotheses address effects of transaction characteristics, of social embeddedness, and of contractual governance on the occurrence of problems. Other than earlier research on embeddedness effects in this field, we consider not only effects of dyadic embeddedness but also effects of network embeddedness. We test hypotheses using rich survey data on more than 1200 purchases of information technology (IT) products: hardware and software, both standard and complex. We find evidence for effects of transaction characteristics on the occurrence of problems, while our data do not support hypotheses on effects of contractual governance. Our data provide rather consistent support for hypotheses on the effects of embeddedness. Specifically, we find evidence that network embeddedness reduces problems. Copyright Springer Science+Business Media, Inc. 2006buyer–supplier relations, embeddedness, ex post problems, inter-firm networks, governance, transaction cost theory,