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Microalgae III: Stress Response and Wastewater Remediation
Published in Arun Kumar, Jay Shankar Singh, Microalgae in Waste Water Remediation, 2021
In low Fe availability, many cyanobacteria and microalgae show a decrease in the ferredoxin level, an iron-containing component of the electron transport chain, but there is a subsequent increase in flavodoxin level, a non-iron-containing electron carrier (Bottin and Lagoutte 1992, McKay et al. 1999). Further high Fe availability may also induce an oxidative stress that could lead to various physiological changes. There could be a reaction of Fe2+ with H2O2(produced by the microalgal cells themselves), which take place inside the cell to produce hydroxyl radicals (OH-) through the Fenton reaction: Fe(III)+O2−→Fe(II)+O2−H2O2+Fe(II)→OH−+OH−+Fe(III)
On the influence of dimerisation of lumiflavin in aqueous solution on its optical spectra – a quantum chemical study
Published in Molecular Physics, 2019
Daria Brisker-Klaiman, Andreas Dreuw
Flavins are known to form dimers in solution. It was demonstrated that flavin mononucleotide (FMN) forms dimers in various solvents, including water, but does not form higher aggregates even in high concentrations (see e.g. [19] and references therein). Flavin dimers, stacked through π–π interactions were also shown to occur in several biological systems. For example, Dodecin, a protein that exists in both archaea and bacteria, binds flavin dimers as its substrate to protect them from photodegradation [20]. Binding of FMN dimers was also found in flavodoxin, a bacterial flavoproteins that participate in electron transfer pathways [21].
Bioprocessing of recombinant proteins from Escherichia coli inclusion bodies: insights from structure-function relationship for novel applications
Published in Preparative Biochemistry & Biotechnology, 2023
Kajal Kachhawaha, Santanu Singh, Khyati Joshi, Priyanka Nain, Sumit K. Singh
Such insoluble aggregate formation can be prevented by slowing down the protein synthesis rate by using a weak promoter, using a low copy number plasmid, or production at lower temperatures and extreme pH ranges.[54] Culture conditions can be manipulated to slow down or enhance the expression of recombinant protein in E. coli. Reducing the growth temperature may help decrease the formation of inclusion bodies because of the slower protein synthesis rate.[72] Moreover, the decrease in temperature prevents aggregation by reducing the hydrophobic interactions.[73] Reduced temperature can also be responsible for the prolonged induction time, increasing the expressed protein’s solubility.[58] This is due to the inactivity of most of the proteases at lower temperatures, so they cannot cleave or degrade newly synthesized proteins.[72] Several studies report the improvement in expression of recombinant protein in E. coli with the reduction in incubation temperature. Huang et al., reported improvement in protein folding when the incubation temperature was decreased from 37 °C to 25 °C. This led to an increase in the yield of nonstructural antigen protein 3 of the hepatitis C virus in E. coli from 4.15 to 11.1 mg/L.[74] In another study, higher fraction of soluble anti-HER2 scFv was attained when the E. coli culture was carried out at 25 °C.[75] pH is also known to play an important role in the correct folding of recombinant protein. pH manipulation influences IB formation and their physical as well as chemical characteristics. Thus, pH should be optimized in such a way that IB formation can be minimized. Li and Cheng reported an increase in the aggregation of blue fluorescent protein with decrease in pH.[76] In contrast, an increase in the culture pH was shown to increase the formation of inclusion bodies during salmon growth hormone (SGH) production using E. coli.[77] The addition of cofactors in the growth medium may also help in the proper folding of some proteins, and a change in pH can affect the proteolytic activity and secretion of specific proteins. It has been reported that addition of FMN in the unfolded form of flavodoxin speeds up its folding process by several times.[78] In another study, the presence of metallic cofactor Ca2+ hemin was found to positively influence the refolding of horseradish peroxidase.[79]