Control of piezoelectricity in amino acids by supramolecular packing.

Piezoelectricity, the linear relationship between stress and induced electrical charge, has attracted recent interest due to its manifestation in biological molecules such as synthetic polypeptides or amino acid crystals, including gamma (γ) glycine. It has also been demonstrated in bone, collagen, elastin and the synthetic bone mineral hydroxyapatite. Piezoelectric coefficients exhibited by these biological materials are generally low, typically in the range of 0.1-10 pm V-1, limiting technological applications. Guided by quantum mechanical calculations we have measured a high shear piezoelectricity (178 pm V-1) in the amino acid crystal beta (ß) glycine, which is of similar magnitude to barium titanate or lead zirconate titanate. Our calculations show that the high piezoelectric coefficients originate from an efficient packing of the molecules along certain crystallographic planes and directions. The highest predicted piezoelectric voltage constant for ß-glycine crystals is 8 V mN-1, which is an order of magnitude larger than the voltage generated by any currently used ceramic or polymer.

Structure of caa(3) cytochrome c oxidase--a nature-made enzyme-substrate complex.

Aerobic respiration, the energetically most favorable metabolic reaction, depends on the action of terminal oxidases that include cytochrome c oxidases. The latter forms a part of the heme-copper oxidase superfamily and consists of three different families (A, B, and C types). The crystal structures of all families have now been determined, allowing a detailed structural comparison from evolutionary and functional perspectives. The A2-type oxidase, exemplified by the Thermus thermophilus caa(3) oxidase, contains the substrate cytochrome c covalently bound to the enzyme complex. In this article, we highlight the various features of caa(3) enzyme and provide a discussion of their importance, including the variations in the proton and electron transfer pathways.

Effective Cancer Theranostics with Polymer Encapsulated Superparamagnetic Nanoparticles: Combined Effects of Magnetic Hyperthermia and Controlled Drug Release.

A combination of chemotherapy with nonconventional nanoparticle based physical destruction therapy has been proposed clinically to reduce the prospect of evolution of drug resistance in cancer. Superparamagnetic nanoparticles have been actively used for synergetic cancer therapy including magnetic fluid hyperthermia (MFH) guided by magnetic resonance imaging (MRI). To explore this direction of potential applications in cancer therapy, we have functionalized superparamagnetic La0.7Sr0.3MnO3 nanoparticles (SPMNPs) with an oleic acid-polyethylene glycol (PEG) polymeric micelle (PM) structure, and loaded it with anticancer cancer drug doxorubicin (DOX) in a high loading capacity (∼60.45%) for in vitro delivery into cancer cells. The micellar structure provided good colloidal stability and biocompatibility. Upon drug loading, the cancer cell death rate of 89% was comparable to free DOX (75%) for 24 h, and that the counterstrategy of DOX conjugated SPMNPs-induced hyperthermia resulted the cancer cell extinction up to 80% under in vitro conditions within 30 min. In addition, the preliminary effect of protein corona formation on in vitro drug release and delivery was studied. Finally, in vivo bio distribution of micellar SPMNPs is observed in mice model for 50 mg kg-1 dose of SPMNPs. Taken together, polymeric micelle SPMNPs reported here can serve as a promising candidate for effective multimodal cancer theranostics such as in the combined chemotherapy-hyperthermia cancer therapy.

The structure of a ferrous heme-nitro species in the binuclear heme a3/CuB center of ba3-cytochrome c oxidase as determined by resonance Raman spectroscopy.

Members of the cytochrome c oxidase family exhibit nitrite reductase activity. In this work, we have characterized a ferrous heme a3-nitro species in ba3-oxidase by resonance Raman spectroscopy. This provides the first evidence for the structure of a nitrite-bound species in the binuclear heme/copper center of cytochrome c oxidases.

Observation of ligand transfer in ba3 oxidase from Thermus thermophilus: simultaneous FTIR detection of photolabile heme a3(2+)-CN and transient Cu(B)(2+)-CN complexes.

FTIR and light-minus-dark FTIR spectroscopy have been employed to investigate the reaction of oxidized and fully reduced ba(3) oxidase with cyanide. The characterization of the structures of the bound CN(-) in the binuclear heme Fe-Cu(B) center is essential, given that a central issue in the function of ba(3) oxidase is the extent to which the partially reduced substrates interact with the two metals. In the reaction of oxidized ba(3) oxidase with cyanide the initially formed heme a(3)(3+)-C≡N-Cu(B)(2+) species with ν(CN) frequency at 2152 cm(-1) was replaced by a photolabile complex with a frequency at 2075 cm(-1) characteristic of heme a(3)(2+)-CN(-). Photolysis of the heme a(3)(2+)-CN(-) adduct produced a band at 2146 cm(-1) attributed to the formation of a transient Cu(B)(2+)-CN(-) complex. All forms are pH independent between pH 5.5-9.5 and at pD 7.5 indicating the absence of ionizable groups that influence the properties of the cyanide complexes. In contrast to previous reports, our results show that CN(-) does not bind simultaneously to both heme a(3)(2+) and Cu(B)(2+) to form the mixed valence a(3)(2+)-CN·Cu(B)(2+)CN species. The photolysis products of the heme a(3)(2+)-CN(-)/Cu(B)(2+) and heme a(3)(2+)-CN(-)/Cu(B)(1+) species are different suggesting that relaxation dynamics in the binuclear center following ligand photodissociation are dependent on the oxidation state of Cu(B).