A Molecular Magnet Confined in the Nanocage of a Globular Protein

• Published in: Chemphyschem 2010-02, Vol.11 (2), p.389-393
• Main Authors: Mitra, Rajib K., Verma, Pramod K., Wulferding, Dirk, Menzel, Dirk, Mitra, Tamoghna, Todea, Ana M., Lemmens, Peter, Müller, Achim, Pal, Samir K.
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Binding Sites; Biological and medical sciences; Energy Transfer; Fundamental and applied biological sciences. Psychology; Humans; magnetic properties; Magnetics; Miscellaneous; molecular dynamics; Molecular Structure; Protein Binding; Protein Conformation; Protein Folding; protein structures; Proteins; Serum Albumin - chemistry; Spectrometry, Fluorescence; Temperature; Thermodynamics; vanadates
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.200900708

The effect of confinement and energy transfer on the dynamics of a molecular magnet, known as a model system to study quantum coherence, is investigated. For this purpose the well‐known polyoxovanadate [V15As6O42(H2O)]6− (V15) is incorporated into a protein (human serum albumin, HSA) cavity. Due to a huge overlap of the optical absorption spectrum of V15 with the emission spectrum of a fluorescence center of HSA (containing a single tryptophan residue), energy transfer is induced and probed by steady‐state and time‐resolved fluorescence. The geometrical coordination and the distance of the confined V15 to the tryptophan moiety of HSA are investigated at various temperatures. This effect is used as a local probe for the thermal denaturation of the protein at elevated temperatures. Confined spaces: The complexation and confinement of [V15As6O42(H2O)]−6 (V15) in the cavity of human serum albumin (HSA) leads to enhanced stability without perturbing the magnetic properties of V15 or the tertiary structure of the protein. Resonance energy transfer via excited‐state dipole–dipole interaction is probed by steady‐state and time‐resolved fluorescence spectroscopy of the HSA (see picture).