Effects of metal and the phytyl chain on chlorophyll derivatives: physicochemical evaluation for photodynamic inactivation of microorganisms

Chlorophyll compounds and their derivatives containing metal or phytyl chain can be used as photosensitizer in photodynamic inactivation of microorganisms (PDI). So, the physicochemical properties and antimicrobial effect of chlorophyll derivatives were investigated: Mg‐chlorophyll (Mg‐Chl), Zn‐chlorophyll (Zn‐Chl), Zn‐chlorophyllide (Zn‐Chlde), Cu‐chlorophyll (Cu‐Chl), pheophytin (Pheo) and pheophorbide (Pheid). The photobleaching experiments showed photostability according to Cu‐Chl > Pheo ∼ Pheid ≫ Zn‐Chl ∼ Zn‐Chlde > Mg‐Chl. This order was discussed in terms of metal and the phytyl chain presences. Pheid and Zn‐Chl in aqueous Tween 80 solution exhibited highest singlet oxygen yield compared with the other derivatives. Chlorophyll derivatives (CD) with phytyl chain was limited by the self‐aggregation phenomenon at high concentrations, even in micellar systems (Tween 80 and P‐123). The antimicrobial effect of CD derivatives was investigated against Staphylococcus aureus, Escherichia coli, Candida albicans and Artemia salina. Pheid showed the best results against all organisms tested, Zn‐Chlde was an excellent bactericide in the dark and Cu‐Chl had no PDI effect. No correlation with CD uptake by microorganisms and darkness cytotoxicity was found. The physicochemical properties allied to bioassays results indicate that Mg‐Chl, Pheo, Zn‐Chl and Pheid are good candidates for PDI.     

Catalyst control in sequential asymmetric allylic substitution: stereodivergent access to N,N-diprotected unnatural amino acids

The sequential use of Cu-catalyzed asymmetric allylic alkylation, olefin cross-metathesis, and Ir-catalyzed asymmetric allylic amination allows the concise, stereodivergent synthesis of complex chiral amines with complete regiocontrol and good diastereoselectivity, exemplified by the synthesis of a pair of diastereoisomeric unnatural branched amino acid derivatives.     

Amplitudes for astrophysicists: known knowns

The use of quantum field theory to understand astrophysical phenomena is not new. However, for the most part, the methods used are those that have been developed decades ago. The intervening years have seen some remarkable developments in computational quantum field theoretic tools. In particle physics, this technology has facilitated calculations that, even ten years ago would have seemed laughably difficult. It is remarkable, then, that most of these new techniques have remained firmly within the domain of high energy physics. We would like to change this. As alluded to in the title, this paper is aimed at showcasing the use of modern on-shell methods in the context of astrophysics and cosmology. In this article, we use the old problem of the bending of light by a compact object as an anchor to pedagogically develop these new computational tools. Once developed, we then illustrate their power and utility with an application to the scattering of gravitational waves.     

Reactivity Tuning of Metal-Free Artificial Photoenzymes through Binding Site Specific Bioconjugation

The design and development of artificial metal-free photoenzymes aims to combine the selectivity of enzymatic reactions with the benefits of modern synthetic photocatalysts. Removing the need for rare earth metals and allowing for milder reaction conditions, leading to a more sustainable catalytic system. Here, we present the design of a novel artificial photoenzyme by integrating an organophotocatalytic moiety based on a donor-acceptor design into a steroid carrier protein (SCP-2L). SCP-2L possesses a hydrophobic tunnel facilitating substrate binding in aqueous media. The photocatalyst was site-selectively bound to three SCP-2L variants, possessing a non-native cysteine residue strategically placed around the hydrophobic tunnel of the protein. The three modified photoenzymes were shown to be selective for the oxidation of organic sulfides giving up to 192 turnovers.     

Confirmation of n-Hexane as an Inert Co-Solvent in the Production of Functionalized Silicon Nanoparticles from Reactive High-Energy Ball Milling

Alkanes such as n-hexane have been used as co-solvents in the production of functionalized semiconductor nanoparticles from alkenes and alkynes using Reactive High Energy Ball Milling (RHEBM) under the assumption that they are non-reactive under typical milling conditions. In this paper, a comparative study with two hydrocarbon solvents of comparable chain length, 1-hexyne, and n-hexane, and their milling products using three different commercially available silicon precursors, namely single crystal silicon wafers and polycrystalline particles having a nominal size of 4 µm and 1 mm, is reported. It is found that nanoparticle formation and surface functionalization in all the three silicon systems occurs only with 1-hexyne; n-hexane is non-reactive and does not lead to appreciable functionalized nanoparticle formation under the conditions studied. Nanoparticles (where formed) and microparticle byproducts of appropriate samples are characterized by Transmission electronic microscope (TEM), Fourier transform infrared  (FTIR), Photoluminiscence spectroscopy (PL), Nuclear magnetic resonance ¹H/¹³C NMR, and thermogravimetry TGA to separately confirm nanoparticle formation and surface functionalization.     

A voltammetric method for diuron determination in river water

A sensitive, simple, fast, and inexpensive method for determining diuron in water using square wave voltammetry and a glassy carbon electrode is presented. This method was developed to evaluate diuron contamination in river waters close to sugarcane cultivation, located in the metropolitan region of João Pessoa, in the state of Paraíba, Brazil. An analytical curve with a linear response ranging from 38.5–115.0 nmol L⁻¹ (r² = 0.993), a LOD equal 0.2 nmol L⁻¹, and recovery rates from 88.0 to 108.0 %. The proposed method does not require any previous chemical treatment of the sample, thus contributing to green analytical chemistry.     

Crystalline Nanoparticles of Water-Soluble Covalent Basket Cages (CBCs) for Encapsulation of Anticancer Drugs

We herein describe the preparation, assembly, recognition characteristics, and biocompatibility of novel covalent basket cage CBC- 11 , composed of four molecular baskets linked to four trivalent aromatic amines through amide groups. The cage is tetrahedral in shape and similar in size to small proteins (M_w=8637 g/mol) with a spacious nonpolar interior for accommodating multiple guests. While 24 carboxylates at the outer surface of CBC- 11 render it soluble in aqueous phosphate buffer (PBS) at pH=7.0, the amphiphilic nature prompts its assembly into nanoparticles (d=250 nm, DLS). Cryo-TEM examination of nanoparticles revealed their crystalline nature with wafer-like shapes and hexagonally arranged cages. Nanoparticulate CBC- 11 traps anticancer drugs irinotecan and doxorubicin, with each cage binding up to four drug molecules in a non-cooperative manner. The inclusion complexation resulted in nanoparticles growing in size and precipitating. In media containing mammalian cells (HCT 116, human colon carcinoma), the IC₅₀ value of CBC- 11 was above 100 μM. While this work presents the first example of a large covalent organic cage operating in water at the physiological pH and forming crystalline nanoparticles, it also demonstrates its biocompatibility and potential to act as a polyvalent binder of drugs for their sequestration or delivery.