Role of Cationic Side Chains in the Antimicrobial Activity of C18G.

Antimicrobial peptides (AMPs) have been an area of great interest, due to the high selectivity of these molecules toward bacterial targets over host cells and the limited development of bacterial resistance to these molecules throughout evolution. The peptide C18G has been shown to be a selective, broad spectrum AMP with a net +8 cationic charge from seven lysine residues in the sequence. In this work, the cationic Lys residues were replaced with other natural or non-proteinogenic cationic amino acids: arginine, histidine, ornithine, or diaminopropionic acid. These changes vary in the structure of the amino acid side chain, the identity of the cationic moiety, and the pKa of the cationic group. Using a combination of spectroscopic and microbiological methods, the influence of these cationic groups on membrane binding, secondary structure, and antibacterial activity was investigated. The replacement of Lys with most other cationic residues had, at most, 2-fold effects on minimal inhibitory concentration against a variety of Gram-positive and Gram-negative bacteria. However, the peptide containing His as the cationic group showed dramatically reduced activity. All peptide variants retained the ability to bind lipid vesicles and showed clear preference for binding vesicles that contained anionic lipids. Similarly, all peptides adopted a helical conformation when bound to lipids or membrane mimetics, although the peptide containing diaminopropionic acid exhibited a decreased helicity. The peptides exhibited a wider variety of activity in the permeabilization of bacterial membranes, with peptides containing Lys, Arg, or Orn being the most broadly active. In all, the antibacterial activity of the C18G peptide is generally tolerant to changes in the structure and identity of the cationic amino acids, yielding new possibilities for design and development of AMPs that may be less susceptible to immune and bacterial recognition or in vivo degradation

The Impact of the COVID-19 Pandemic on Women's Perinatal Mental Health: Preliminary Data on the Risk of Perinatal Depression/Anxiety from a National Survey in Italy

Increasing evidence suggests that during the COVID-19 pandemic, anxiety and depression during the perinatal period increased. The aim of the study is to estimate the prevalence of risk for both maternal depression and anxiety among women attending 18 healthcare centres in Italy during the SARS-COV-2 pandemic and to investigate the psychosocial risks and protective factors associated. It was divided into a retrospective phase (2019, 2020, and the first nine months of 2021) and a prospective phase (which began in November 2021 and it is still ongoing), which screened 12,479 and 2349 women, respectively, for a total of 14,828 women in the perinatal period. To evaluate the risk of anxiety and depression, the General Anxiety Disorder-7 (GAD-7), the Edinburgh Postnatal Depression Scale (EPDS), and an ad hoc form were used to collect sociodemographic variables. In the prospective study, the average age of the women is 31 (range 18-52) years. Results showed that the percentage of women who had EPDS score ≥9 increased from 11.6% in 2019 to 25.5% in the period ranging from November 2021 to April 2022. In logistic regression models, the variables associated with the risk of depression at a level ≤0.01 include having economic problems (OR 2.16) and not being able to rely on support from relatives or friends (OR 2.36). Having the professional status of the housewife is a lower risk (OR 0.52). Those associated with the risk of anxiety include being Italian (OR 2.97), having an education below secondary school level (OR 0.47), having some or many economic problems (OR 2.87), being unable to rely on support from relatives or friends (OR 2.48), and not having attended an antenatal course (OR 1.41). The data from this survey could be useful to determine the impact of the SARS-COV-2 pandemic on women and to establish a screening program with common and uniformly applied criteria which are consistent with national and international women's mental health programs

THE BIOCHEMISTRY AND STRUCTURE OF A NOVEL NITRIC OXIDE SYNTHASE FROM CYANOBACTERIA

135 pagesNitric oxide synthases (NOS) are monooxygenase enzymes that catalyze the oxidation of L-arginine to L-citrulline and nitric oxide (NO). They are composed of a catalytic heme binding domain (NOSox) and a flavin-binding domain (NOSred) responsible for electron transfer and heme activation. NOS-derived NO serves as a signaling molecule in animals, controlling vascular tone, immune response, and neuronal signaling. NOS are also found in bacteria and are involved in various roles, including biofilm formation, recovery from UV damage, and protection from oxidative stress. However bacterial NOS sequences only contain a NOSox domain, and must rely on nonspecific reductases for activation. Recently, sequences for a unique NOS-like protein have been identified in cyanobacteria. These proteins are the first bacterial NOS to contain a mammalian-like NOSred, and also contain a globin-like domain (NOSg) which has not been observed in any other NOS. This work confirms that the NOS from the cyanobacteria Synechoccocus sp. PCC 7335 (syNOS) is a true NOS, and produces NO from L-arginine. However, the factors governing syNOS activation deviate from our current knowledge of NOS enzymology. syNOS requires Ca2+ and tetrahydrobiopterin for NO production, and syNOSg rapidly oxidizes all NO to nitrate. syNOSred facilitates the reduction of syNOSox and syNOSg independent of one another, which indicates direct electron transfer between syNOSg and syNOSred. The reduction of syNOSg can also be mediated by syNOSFAD, in a manner analogous to flavohemoglobin proteins, and does not require syNOSFMN, as in NOSox reduction. The structures of syNOSFAD and syNOSFMN have been determined, and homology modeling of syNOSg confirms that syNOSFAD – syNOSg domain interactions are possible. The function of syNOS has yet to be identified, but genomic analysis of other syNOS homologues suggests it may participate in signal transduction pathways. The presence of syNOSg and its Ca2+ dependence may serve as a switch to turn on/off such signaling pathways

Impacts of Hydrophobic Mismatch on Antimicrobial Peptide Efficacy and Bilayer Permeabilization

Antimicrobial resistance continues to be a major threat to world health, with the continued emergence of resistant bacterial strains. Antimicrobial peptides have emerged as an attractive option for the development of novel antimicrobial compounds in part due to their ubiquity in nature and the general lack of resistance development to this class of molecules. In this work, we analyzed the antimicrobial peptide C18G and several truncated forms for efficacy and the underlying mechanistic effects of the sequence truncation. The peptides were screened for antimicrobial efficacy against several standard laboratory strains, and further analyzed using fluorescence spectroscopy to evaluate binding to model lipid membranes and bilayer disruption. The results show a clear correlation between the length of the peptide and the antimicrobial efficacy. Furthermore, there is a correlation between peptide length and the hydrophobic thickness of the bilayer, indicating that hydrophobic mismatch is likely a contributing factor to the loss of efficacy in shorter peptides