Structural and conformational differences of acylated hyaluronan modified in protic and aprotic solvent system

Acylated hyaluronan (HA) in aqueous (DMSO/H₂O) and nonaqueous (DMSO) solutions was studied by means of nuclear magnetic resonance, differential scanning calorimetry (DSC), mass spectrometry and UV/vis spectroscopy. It has been demonstrated that structural and conformational properties of the acylated hyaluronan derivates are strongly dependent on the nature of reaction solvent. Acylation in DMSO was more selective than that carried out in DMSO/H₂O, though in both cases in average a maximum of one acyl chain was detected per HA dimer. The hydrophobic functionalization of hyaluronan induced its interaction with hydrophobic dye as a consequence of acyl chain aggregation. The higher the degree of acylation the more hydrophobic dye was interacting with HA. For concentrated samples, aggregation was more evident in case of acylated HA in aqueous solution. This phenomenon was explained by its different conformational arrangement in solution which was further supported by DSC data indicating an existence of hydrophobic cavities. The formation of self-aggregated assemblies indicates potential applications of this type of HA derivate as drug delivery system.     

Enhancement of antibody functions through Fc multiplications

Antibodies carry out a plethora of functions through their crystallizable fragment (Fc) regions, which can be naturally tuned by the adoption of several isotypes and post-translational modifications. Protein engineering enables further Fc function modulations through modifications of the interactions between the Fc and its functional partners, including FcγR, FcRn, complement complex, and additions of auxiliary functional units. Due to the many functions embedded within the confinement of an Fc, a suitable balance must be maintained for a therapeutic antibody to be effective and safe. The outcome of any Fc engineering depends on the interplay among all the effector molecules involved. In this report, we assessed the effects of Fc multiplication (or tandem Fc) on antibody functions. Using IgG1 as a test case, we found that, depending on the specifically designed linker, Fc multiplication led to differentially folded, stable molecules with unique pharmacokinetic profiles. Interestingly, the variants with 3 copies of Fc improved in vitro opsonophagocytic killing activity and displayed significantly improved protective efficacies in a Klebsiella pneumoniae mouse therapeutic model despite faster clearance compared with its IgG1 counterpart. There was no adverse effect observed or pro-inflammatory cytokine release when the Fc variants were administered to animals. We further elucidated that enhanced binding to various effector molecules by IgG-3Fc created a “sink” leading to the rapid clearance of the 3Fc variants, and identified the increased FcRn binding as one strategy to facilitate “sink” escape. These findings reveal new opportunities for novel Fc engineering to further expand our abilities to manipulate and improve antibody therapeutics.     

Photochemical synthesis of pink silver and its use for monitoring peptide nitration via surface enhanced Raman spectroscopy (SERS)

Oxidative stress may cause extended tyrosine posttranslational modifications of peptides and proteins. The 3-nitro-L-tyrosine (Nit), which is typically formed, affects protein behavior during neurodegenerative processes, such as Alzheimer’s and Parkinson’s diseases. Such metabolic products may be conveniently detected at very low concentrations by surface enhanced Raman spectroscopy (SERS). Previously, we have explored the SERS detection of the Nit NO₂ bending vibrational bands in a presence of hydrogen chloride (Niederhafner et al., Amino Acids 53:517–532, 2021, ibid). In this article, we describe performance of a new SERS substrate, “pink silver”, synthesized photochemically. It provides SERS even without the HCl induction, and the acid further decreases the detection limit about 9 times. Strong SERS bands were observed in the asymmetric (1550–1475 cm^?1) and symmetric (1360–1290 cm^?1) NO stretching in the NO₂ group. The bending vibration was relatively weak, but appeared stronger when HCl was added. The band assignments were supported by density functional theory modeling.

     

Design,synthesis, and in vitro evaluation of BP-1-102 analogs with modified hydrophobic fragments for STAT3 inhibition

Twelve novel analogs of STAT3 inhibitor BP-1-102 were designed and synthesised with the aim to modify hydrophobic fragments of the molecules that are important for interaction with the STAT3 SH2 domain. The cytotoxic activity of the reference and novel compounds was evaluated using several human and two mouse cancer cell lines. BP-1-102 and its two analogs emerged as effective cytotoxic agents and were further tested in additional six human and two murine cancer cell lines, in all of which they manifested the cytotoxic effect in a micromolar range. Reference compound S3I-201.1066 was found ineffective in all tested cell lines, in contrast to formerly published data. The ability of selected BP-1-102 analogs to induce apoptosis and inhibition of STAT3 receptor-mediated phosphorylation was confirmed. The structure–activity relationship confirmed a demand for two hydrophobic substituents, i.e. the pentafluorophenyl moiety and another spatially bulky moiety, for effective cytotoxic activity and STAT3 inhibition.     

Altitudinal distribution and diversity of insects in miombo woodlands in Inhamacari,Manica Province,central Mozambique

To evaluate the role of altitude on distribution pattern and diversity of entomofauna on miombo woodlands, four altitudes (850, 1,000, 1,250 and 1,400 m) were selected in a characteristic mountainous forest of Inhamacari in Mozambique in July 2015. In each sampling altitude, a linear transect with 16 yellow pan traps spaced 2 m apart was established for insect capture. Capture results allowed assessment of insect distribution by determination of insect abundance and relative frequency. Insect diversity estimates were determined by Shannon–Wiener and Simpson indices. Altitude similarity was assessed by the Jaccard coefficient. The chi-square test () was used to compare insect abundance and distribution along the altitudinal gradient. Altitude significantly affected insect abundance, relative frequency and distribution, with a nonlinear decrease with increasing altitude. Families Formicidae (Hymenoptera) and Cecidomyiidae (Diptera) were most dominant. Highest diversity and more families confined to unique altitudinal positions were found at 1,250 m while the lowest diversity was observed at 1,000 m.a.s.l. Among the altitudes, greater similarity was found between 1,000 and 1,400 m. In conclusion, altitude had a significant effect on insect family's distribution. However, further research is recommended in order to understand effect of vegetation composition and structure on insect diversity at different altitudes.     

Impaired leptin activity in New Zealand Obese mice: model of angiogenesis

Leptin is prompt to drive angiogenesis, effecting proper vascularisation. Tissue remodeling (including adipose organ) is associated with the angiogenic response. The aim of this study was to investigate the effect of hyperleptinemia on angiogenesis in subcutaneous (s.c.) in vivo matrigel model in mice on a high fat (HF) diet. HF promoted adipose tissue accumulation and biochemical changes resembling metabolic syndrome. However, the impact of this dietary treatment on angiogenesis, measured in s.c. matrigel model was not significant. Changes in leptin concentration were not accompanied by significant angiogenic response. This lack of leptin activity and impaired signal transduction at the molecular level suggests malfunction of the leptin receptor in NZO mice.     

The cps gene cluster of Salmonella strain LT2 includes a second mannose pathway: sequence of two genes and relationship to genes in the rfb gene cluster

Summary We report the presence in Salmonella enterica strain LT2 (serovar thyphimurium) of duplicate genes for two steps in the synthesis of GDP-mannose. The previously known genes, rfbK (phosphomannomutase) and rfbM (mannose-l-phosphate guanyltransferase), are part of the gene cluster for the O antigen. The two new genes, cpsB and cpsG, respectively, are thought to be part of the gene cluster for the M antigen capsular polysaccharide, present in many Enterobacteriaceae. The two genes have been sequenced and have a GC content of 0.61, suggesting an origin outside of Salmonella. Comparison of the inferred protein sequences for cpsB and rfbM shows 57% identity of amino acids whereas for cpsG and rfbK there is only 19% identity. It is suggested that the greater divergence between cpsG and rfbK may be due to a period of accelerated evolution, perhaps precipitated by transfer of the genes from another species.