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1. Synthesis of Lysine Mimicking Membrane Active Antimicrobial Polymers

   Ankita Arora; Wan Zheng; Hongjun Liang; Abhijit Mishra (November 2018, Advances in Polymer Sciences and Technology)

   Bhuvanesh Gupta; Anup K.Ghosh; Atsushi Suzuki; Sunita Rattan (Ed.)

   Antibiotic resistance in bacteria is a major health concern. Antimicrobial Peptides (AMPs) are efficient in killing most microbes and yet the development of resistance to AMPs is rare. Although AMPs show promising antimicrobial activities, commercializing them as antibiotics is difficult as in vitro extraction and purification of AMPs is complicated and expensive. AMP mimicking antimicrobial polymers can overcome such problems while maintaining the necessary features of AMPs. Here, we have developed meth-acrylamide based polymers to mimic AMPs which possess high antimicrobial activities with low cytotoxicity. Bactericidal and scanning electron microscopy studies show that the synthesized polymers are effective against Gram-positive and Gram-negative bacteria. We find that these polymers are lethal to bacteria and at the same time, they are also non-cytotoxic to mammalian cells, thereby increasing the potential of these polymers to be used as antibiotics. 

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2. Modification of narrow‐spectrum peptidomimetic polyurethanes with fatty acid chains confers broad‐spectrum antibacterial activity

   https://doi.org/10.1002/pi.5773  

   Peng, Chao; Zhang, Tian; Ortiz‐Ortiz, Deliris_N; Vishwakarma, Apoorva; Barton, Hazel_A; Joy, Abraham (February 2019, Polymer International)

   Abstract Each year, thousands of patients die from antimicrobial‐resistant bacterial infections that fail to respond to conventional antibiotic treatment. Antimicrobial polymers are a promising new method of combating antibiotic‐resistant bacterial infections. We have previously reported the synthesis of a series of narrow‐spectrum peptidomimetic antimicrobial polyurethanes that are effective against Gram‐negative bacteria, such asEscherichia coli; however, these polymers are not effective against Gram‐positive bacteria, such asStaphylococcus aureus. With the aim of understanding the correlation between chemical structure and antibacterial activity, we have subsequently developed three structural variants of these antimicrobial polyurethanes using post‐polymerization modification with decanoic acid and oleic acid. Our results show that such modifications converted the narrow‐spectrum antibacterial activity of these polymers into broad‐spectrum activity against Gram‐positive species such asS. aureus, however, also increasing their toxicity to mammalian cells. Mechanistic studies of bacterial membrane disruption illustrate the differences in antibacterial action between the various polymers. The results demonstrate the challenge of balancing antimicrobial activity and mammalian cell compatibility in the design of antimicrobial polymer compositions. © 2019 Society of Chemical Industry 

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3. A possible distance bias for type Ia supernovae with different ejecta velocities

   https://doi.org/10.1093/mnras/staa577  

   Siebert, M R; Foley, R J; Jones, D O; Davis, K W (April 2020, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT After correcting for their light-curve shape and colour, Type Ia supernovae (SNe Ia) are precise cosmological distance indicators. However, there remains a non-zero intrinsic scatter in the differences between measured distance and that inferred from a cosmological model (i.e. Hubble residuals or HRs), indicating that SN Ia distances can potentially be further improved. We use the open-source relational data base kaepora to generate composite spectra with desired average properties of phase, light-curve shape, and HR. At many phases, the composite spectra from two subsamples with positive and negative average HRs are significantly different. In particular, in all spectra from 9 d before to 15 d after peak brightness, we find that SNe with negative HRs have, on average, higher ejecta velocities (as seen in nearly every optical spectral feature) than SNe with positive HRs. At +4 d relative to B-band maximum, using a sample of 62 SNe Ia, we measure a 0.091 ± 0.035 mag (2.7σ) HR step between SNe with Si ii λ6355 line velocities ($$v_{Si\, rm{\small II}}$$) higher/lower than −11 000 km s−1 (the median velocity). After light-curve shape and colour correction, SNe with higher velocities tend to have underestimated distance moduli relative to a cosmological model. The intrinsic scatter in our sample reduces from 0.094 to 0.082 mag after making this correction. Using the Si ii λ6355 velocity evolution of 115 SNe Ia, we estimate that a velocity difference >500 km s−1 exists at each epoch between the positive-HR and negative-HR samples with 99.4 per cent confidence. Finally at epochs later than +37 d, we observe that negative-HR composite spectra tend to have weaker spectral features in comparison to positive-HR composite spectra. 

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4. Effect of solvent quality and sidechain architecture on conjugated polymer chain conformation in solution

   https://doi.org/10.1039/d3nr05721f  

   Ma, Guorong; Li, Zhaofan; Fang, Lei; Xia, Wenjie; Gu, Xiaodan (March 2024, Nanoscale)

   The solubilization of conjugated polymers can be carefully quantified using static light scattering. Our findings reveal that the architecture of sidechains and backbones significantly influences polymer's conformation and aggregation. 

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5. Unexpected Enhancement of Antimicrobial Polymer Activity against Staphylococcus aureus in the Presence of Fetal Bovine Serum

   https://doi.org/10.3390/molecules26154512  

   Sovadinová, Iva; Kuroda, Kenichi; Palermo, Edmund F. (August 2021, Molecules)

   Cationic and amphiphilic polymers are known to exert broad-spectrum antibacterial activity by a putative mechanism of membrane disruption. Typically, nonspecific binding to hydrophobic components of the complex biological milieu, such as globular proteins, is considered a deterrent to the successful application of such polymers. To evaluate the extent to which serum deactivates antibacterial polymethacrylates, we compared their minimum inhibitory concentrations in the presence and absence of fetal bovine serum. Surprisingly, we discovered that the addition of fetal bovine serum (FBS) to the assay media in fact enhances the antimicrobial activity of polymers against Gram-positive bacteria S. aureus, whereas the opposite is the case for Gram-negative E. coli. Here, we present these unexpected trends and develop a hypothesis to potentially explain this unusual phenomenon. 

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