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Physicochemical properties of two atypical cytochromes c, Crithidia cytochrome c-557 and Euglena cytochrome c-558.

ABSTRACT: Cytochrome c-557 from Crithidia oncopelti and cytochrome c-558 from Euglena gracilis are mitochondrial cytochromes c that have an atypical haem-binding site. It was of interest to know whether the loss of one thioether bond affected the physicochemical properties of these cytochromes. The thermodynamic parameters of the redox potential were measured. The reaction with imidazole, the kinetics and thermodynamics of the alkaline isomerization and the effect of heating on the visible spectrum are described for the ferricytochromes. The kinetics of the loss of cyanide, the spectral changes occurring on reduction with dithionite at alkaline pH values and the reactivity with CO are described for the ferrocytochromes. In many respects the cytochromes of the two protozoans are very similar to the cytochromes of horse and yeast. The ferricytochromes do, however, undergo a reversible transition to high-spin species on heating, which may be due to the more flexible attachment of the prosthetic group. Similarly the alkaline isomers of cytochromes c-557 and c-558 give rise to high-spin proteins above pH 11. The alkaline isomerization of cytochrome c-558, involves a pKobs. of 10 and kinetics which do not obey the model of Davis et al. [(1974) J. Biol. Chem. 249, 2624-2632] for horse cytochrome c. It is proposed that a model involving two ionizations, followed by a conformation change, may fit the data. Both cytochromes c-557 and c-558 combine slowly with CO at neutral pH values.

SUBMITTER: Pettigrew GW

PROVIDER: S-EPMC1165602 | biostudies-other | 1975 Jul

REPOSITORIES: biostudies-other

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Project description:Carbon nanomaterials have shown great potential in several fields, including biosensing, bioimaging, drug delivery, energy, catalysis, diagnostics, and nanomedicine. Recently, a new class of carbon nanomaterials, carbon dots (CDs), have attracted much attention due to their easy and inexpensive synthesis from a wide range of precursors and fascinating physical, chemical, and biological properties. In this work we have developed CDs derived from olive solid wastes of two Mediterranean regions, Puglia (CDs_P) and Calabria (CDs_C) and evaluated them in terms of their physicochemical properties and antibacterial activity against Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). Results show the nanosystems have a quasi-spherical shape of 12-18 nm in size for CDs_P and 15-20 nm in size for CDs_C. UV-Vis characterization indicates a broad absorption band with two main peaks at about 270 nm and 300 nm, respectively, attributed to the π-π* and n-π* transitions of the CDs, respectively. Both samples show photoluminescence (PL) spectra excitation-dependent with a maximum at λem = 420 nm (λexc = 300 nm) for CDs_P and a red-shifted at λem = 445 nm (λexc = 300 nm) for CDs_C. Band gaps values of ≈ 1.48 eV for CDs_P and ≈ 1.53 eV for CDs_C are in agreement with semiconductor behaviour. ζ potential measures show very negative values for CDs_C compared to CDs_P (three times higher, -38 mV vs. -18 mV at pH = 7). The evaluation of the antibacterial properties highlights that both CDs have higher antibacterial activity towards Gram-positive than to Gram-negative bacteria. In addition, CDs_C exhibit bactericidal behaviour at concentrations of 360, 240, and 120 µg/mL, while lesser activity was found for CDs_P (bacterial cell reduction of only 30% at the highest concentration of 360 µg/mL). This finding was correlated to the higher surface charge of CDs_C compared to CDs_P. Further investigations are in progress to confirm this hypothesis and to gain insight on the antibacterial mechanism of both cultivars.

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Physicochemical properties of two atypical cytochromes c, Crithidia cytochrome c-557 and Euglena cytochrome c-558.

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