Reversible oxygenation of oxygen transport proteins

A lecture demonstration illustrating changes in the visible spectra of oxygen transport proteins upon reversihle oxygen binding is reported. The coloration upon exposure to oxygen is dramatic. Deoxyhemoglobin changes from purple to red, deoxyhemocyanin is transformed from colorless to blue, while colorless deoxyhemerythrin turns red. This demonstration illustrates an interesting example of a chemically reversible reaction and is used in the discussion of basic thermodynamic properties. A comparison of the physical characteristics of these oxveen storaee and transn.o rt ~ro- A teins is provided to illustrate the stru&ral diversity associated with these proteins having a similar biological role

Ni(II) (dioxo[16]aneN5)-Induced Methane Formation from Methyl Coenzyme M

The nickel tetrapyrrole containing factor, F430, is implicated in the final methane evolution step in methanogenic ba~terial-~ and has attracted considerable a t t e n t i ~ n . ~T- ~he essential role of F430 in methane formation was demonstrated by Ankel-Fuchs and Thauer, who reported the in vitro catalysis of H3CSCH2CH2S03-, methyl coenzyme M (methyl-CoM), to methane and CoM by purified methyl-CoM reductase under reducing condit i o n ~ .S~in ce F,,o exists in both the Ni(1) (or Ni(II1)) and the Ni(I1) states in Methanobacterium thermoautotrophicum,loi,t ll is of interest to examine the role of the nickel ion oxidation stateI2.l3 in methyl-CoM catalysis. We have found both the mono- and the divalent oxidation states of the water-soluble Ni(dioxo[ 161- aneNS), NiL, complexI4 catalyze methyl-CoM to methane and CoM

Chelator-Free Radiolabeling of SERRS Nanoparticles for Whole-Body PET and Intraoperative Raman Imaging

A single contrast agent that offers whole-body non-invasive imaging along with the superior sensitivity and spatial resolution of surface-enhanced resonance Raman scattering (SERRS) imaging would allow both pre-operative mapping and intraoperative imaging and thus be highly desirable. We hypothesized that labeling our recently reported ultrabright SERRS nanoparticles with a suitable radiotracer would enable pre-operative identification of regions of interest with whole body imaging that can be rapidly corroborated with a Raman imaging device or handheld Raman scanner in order to provide high precision guidance during surgical procedures. Here we present a straightforward new method that produces radiolabeled SERRS nanoparticles for combined positron emission tomography (PET)-SERRS tumor imaging without requiring the attachment of molecular chelators. We demonstrate the utility of these PET-SERRS nanoparticles in several proof-of-concept studies including lymph node (LN) tracking, intraoperative guidance for LN resection, and cancer imaging after intravenous injection. We anticipate that the radiolabeling method presented herein can be applied generally to nanoparticle substrates of various materials by first coating them with a silica shell and then applying the chelator-free protocol

Nanoparticles as multimodal photon transducers of ionizing radiation

In biomedical imaging, nanoparticles combined with radionuclides that generate Cerenkov luminescence are used in diagnostic imaging, photon-induced therapies, and as activatable probes. In these applications, the nanoparticle is often viewed as a carrier inert to ionizing radiation from the radionuclide. However, certain phenomena such as enhanced nanoparticle luminescence and generation of reactive oxygen species cannot be explained by only Cerenkov luminescence interactions with nanoparticles. Herein, we report methods to examine the mechanisms of nanoparticle excitation by radionuclides, including interactions with Cerenkov luminescence, β particles, and γ radiation. We demonstrate that β scintillation contributes appreciably to excitation and reactivity in certain nanoparticle systems and that excitation of nanoparticles composed of large atomic number atoms by radionuclides generates X-rays, enabling multiplexed imaging through single photon emission computed tomography. These findings demonstrate practical optical imaging and therapy using radionuclides with emission energies below the Cerenkov threshold, thereby expanding the list of applicable radionuclides

Porphyrin nanoparticles as supramolecular systems

Certain applications of supramolecular porphyrinic systems, such as molecular sieves and photonics, rely on precise nanoarchitectural control of the molecules and/or atoms; therefore they require self-assembled systems of discrete arrays and highly ordered crystals. Other applications, such as oxidation catalysts for simple substrates, may be affected by the use of self-organized materials with less supramolecular order. Colloidal porphyrin nanoparticles can be considered self-organized systems that are governed by the principles of supramolecular chemistry. The formation and potential applications of nanoparticles of these chromophores are discussed in this report with special emphasis on the parameters in the methods used to make these materials, and in terms of the supramolecular chemistry. These principles, concepts, and methodologies are applicable to a wide variety of organic dyes. Mais Dieu a choisi celuy qui est le plus parfait, c\u27est à dire celuy qui en même temps le plus simple en hypotheses, et le plus rich en phenomenes. Gottfried Leibniz. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique

Designing supramolecular porphyrin arrays for surface assembly and patterning of optoelectronic materials

Designing nanoscale devices requires a clear understanding of the hierarchical structural organization of the functional material - from the design of the molecule, to how the molecules self-assemble into supramolecular structures, to how mese structures organize on various surfaces. Investigations comparing the structures in solution to the structures found on surfaces such as in thin films, nanoparticles, and nanoarrays, reveal the complex interplay between the energetics of selforganization and the energetics of interactions of supramolecular systems with surfaces. A perspective on the design of porphyrins that self-assemble into discrete supramolecular structures that subsequently self-organize into nanoparticles and films, and some of the factors dictating solution and surface morphology is presented. © 2006 American Chemical Society

Self-organization of self-assembled tetrameric porphyrin arrays on surfaces

The incorporation of designed self-assembled supramolecular structures into devices requires deposition onto surfaces with retention of both structure and function. This remains a challenge and can present a significant barrier to developing devices using self-organizing materials. To examine the role of peripheral groups in the self-organization of self-assembled multiporphyrinic arrays on surfaces, Pd(II)-linked square and Pt(II)-linked trapezoidal tetrameric porphyrin arrays with peripheral tenf-butylphenyl or dodecyl-oxyphenyl functionalities were investigated using various spectroscopies and atomic force microscopy. The Pd(II) assembled squares disassemble upon deposition on glass surfaces, while the Pt(II) assembled trapezoids are more robust and can be routinely cast on these surfaces. The orientation and length of the peripheral alkyl substituents influence the resultant structures on surfaces. The tert-butylphenyl-substituted porphyrin array forms discrete columnar stacks, which assemble in a vertical direction via π-stacking interactions among the macrocycles. The tetrameric porphyrin array with dodecyloxyphenyl groups forms a continuous film via van der Waals interactions among the peripheral hydrocarbon chains. The super-molecules with liquid crystal-forming moieties also form three-dimensional crystalline structures at higher deposition concentrations. These observations clearly demonstrate that the number, position, and nature of the peripheral groups and the supramolecular structure and dynamics, as well as the energetics of interactions with the surface, are of key importance to the two-dimensional and three-dimensional self-organization of assemblies such as porphyrin arrays on surfaces