Synthesis and characterization of the thermal and the solvatochromic properties of heterocyclic azo dyes derived from 5-N,N-dialkylamino-2,2´-bithiophene couplers

A series of heterocyclic azo dyes was synthesized by diazotation of several substituted anilines and coupling with 5-N,N-dialkylamino-2,2´-bithiophenes to give 4-phenylazo-5-N,N-dialkylamino-2,2´-bithiophenes 4-7. This reaction contrasts with the behavior of 5-alkoxy-2,2´-bithiophenes towards aryldiazonium salts which gave 5-phenylazo-5-alkoxy-2,2´-bithiophenes. The thermal stability of the derivatives was evaluated using thermogravimetric analysis. The solvatochromic behaviour of the novel bithiophene azo dyes was investigated in several solvents of different polarity. The experimental results indicate that, the heterocyclic azo dyes 4-7 could be used as thermally stable solvatochromic probes.Fundação para a Ciência e a Tecnologia (FCT

Controllable transport mean free path of light in xerogel matrixes embedded with polystyrene spheres

Xerogel matrices, made by sol-gel techniques, are embedded with polystyrene spheres to promote multiple scattering of light. Varying the concentration of the spheres inside the matrix allows one to adjust the transport mean free path of light inside the material. Coherent backscattering measurements show that a range of transport mean free paths from 90 to 600 nm is easily achieved. The determination of the matrix refractive index permits a direct comparison to multiple scattering and Mie theory. Such tunable diffusive sol-gel derived samples can be further optimized as random laser materials.Comment: Updated figures and correcting typos. 5 pages, 3 figure

Human phenylalanine hydroxylase as the case study

Funding Information: Authors acknowledge Sofarimex, Indústria Química e Farmacêutica SA, Portugal, for all the support concerning freeze-drying studies. This work was supported by FEDER and Fundação para a Ciência e a Tecnologia, I. P. through iMED.ULisboa (Projects UIDB/04138/2020 and UIDP/04138/2020), iNOVA4Health (UIDB/04462/2020, UIDP/04462/2020) and LS4FUTURE Associated Laboratory (LA/P/0087/2020) and research project PTDC/EBB-BIO/101237/2008 and research grant SFRH/BD/47946/2008 (to Paulo R. Lino). This work has also received funding from the National PKU Alliance, USA. The authors would like to thank Luís Miguel Ramos and Cátia Nascimento who contributed to the exploratory research that culminated in the work herein presented. Funding Information: Authors acknowledge Sofarimex, Indústria Química e Farmacêutica SA, Portugal, for all the support concerning freeze-drying studies. This work was supported by FEDER and Fundação para a Ciência e a Tecnologia, I. P. through iMED.ULisboa (Projects UIDB/04138/2020 and UIDP/04138/2020), iNOVA4Health (UIDB/04462/2020, UIDP/04462/2020) and LS4FUTURE Associated Laboratory (LA/P/0087/2020) and research project PTDC/EBB-BIO/101237/2008 and research grant SFRH/BD/47946/2008 (to Paulo R. Lino). This work has also received funding from the National PKU Alliance, USA. Publisher Copyright: © 2023 The Author(s)The structural maintenance of therapeutic proteins during formulation and/or storage is a critical aspect, particularly for multi-domain and/or multimeric proteins which usually exhibit intrinsic structural dynamics leading to aggregation with concomitant loss-of-function. Protein freeze-drying is a widely used technique to preserve protein structure and function during storage. To minimize chemical/physical stresses occurring during this process, protein stabilizers are usually included, their effect being strongly dependent on the target protein. Therefore, they should be screened for on a time-consuming case-by-case basis. Herein, differential scanning fluorimetry (DSF) and isothermal denaturation fluorimetry (ITDF) were employed to screen, among different classes of freeze-drying additives, for the most effective stabilizer of the model protein human phenylalanine hydroxylase (hPAH). Correlation studies among retrieved DSF and ITDF parameters with recovered enzyme amount and activity indicated ITDF as the most appropriate screening method. Biochemical and biophysical characterization of hPAH freeze-dried with ITDF-selected stabilizers and a long-term storage study (12 months, 5 ± 3 °C) showed that the selected compounds prevented protein aggregation and preserved hPAH structural and functional properties throughout time storage. Our results provide a solid basis towards the choice of ITDF as a high-throughput screening step for the identification of protein freeze-drying protectors.publishersversionpublishe

Structure of full-length wild-type human phenylalanine hydroxylase by small angle X-ray scattering reveals substrate-induced conformational stability

Human phenylalanine hydroxylase (hPAH) hydroxylates l-phenylalanine (l-Phe) to l-tyrosine, a precursor for neurotransmitter biosynthesis. Phenylketonuria (PKU), caused by mutations in PAH that impair PAH function, leads to neurological impairment when untreated. Understanding the hPAH structural and regulatory properties is essential to outline PKU pathophysiological mechanisms. Each hPAH monomer comprises an N-terminal regulatory, a central catalytic and a C-terminal oligomerisation domain. To maintain physiological l-Phe levels, hPAH employs complex regulatory mechanisms. Resting PAH adopts an auto-inhibited conformation where regulatory domains block access to the active site. l-Phe-mediated allosteric activation induces a repositioning of the regulatory domains. Since a structure of activated wild-type hPAH is lacking, we addressed hPAH l-Phe-mediated conformational changes and report the first solution structure of the allosterically activated state. Our solution structures obtained by small-angle X-ray scattering support a tetramer with distorted P222 symmetry, where catalytic and oligomerisation domains form a core from which regulatory domains protrude, positioning themselves close to the active site entrance in the absence of l-Phe. Binding of l-Phe induces a large movement and dimerisation of regulatory domains, exposing the active site. Activated hPAH is more resistant to proteolytic cleavage and thermal denaturation, suggesting that the association of regulatory domains stabilises hPAH.publishe

Controllable transport mean free path of light in xerogel matrixes embedded with polystyrene spheres

Xerogel matrices, made by sol-gel techniques, are embedded with polystyrene spheres to promote multiple scattering of light. Varying the concentration of the spheres inside the matrix allows one to adjust the transport mean free path of light inside the material. Coherent backscattering measurements show that a range of transport mean free paths from 90 to 600 nm is easily achieved. The determination of the matrix refractive index permits a direct comparison to multiple scattering and Mie theory. Such tunable diffusive sol-gel derived samples can be further optimized as random laser materials.Comment: Updated figures and correcting typos. 5 pages, 3 figure

Increased variability of motor cortical excitability to transcranial magnetic stimulation in migraine: a new clue to an old enigma

Increased, decreased or normal excitability to transcranial magnetic stimulation (TMS) has been reported in the motor (M1) and visual cortices of patients with migraine. Light deprivation (LD) has been reported to modulate M1 excitability in control subjects (CS). Still, effects of LD on M1 excitability compared to exposure to environmental light exposure (EL) had not been previously described in patients with migraine (MP). To further our knowledge about differences between CS and MP, regarding M1 excitability and effects of LD on M1 excitability, we opted for a novel approach by extending measurement conditions. We measured motor thresholds (MTs) to TMS, short-interval intracortical inhibition, and ratios between motor-evoked potential amplitudes and supramaximal M responses in MP and CS on two different days, before and after LD or EL. Motor thresholds significantly increased in MP in LD and EL sessions, and remained stable in CS. There were no significant between-group differences in other measures of TMS. Short-term variation of MTs was greater in MP compared to CS. Fluctuation in excitability over hours or days in MP is an issue that, until now, has been relatively neglected. The results presented here will help to reconcile conflicting observations.Instituto Israelita de Ensino e Pesquisa Albert Einstein/Arthur Goldlust [143-06]Instituto Israelita de Ensino e Pesquisa Albert Einstein/Arthur Goldlus

Cognitive and Brain Activity Changes After Mnemonic Strategy Training in Amnestic Mild Cognitive Impairment: Evidence From a Randomized Controlled Trial

Background: Mnemonic strategy training (MST) has been shown to improve cognitive performance in amnestic mild cognitive impairment (a-MCI), however, several questions remain unresolved. The goal of the present study was to replicate earlier pilot study findings using a randomized controlled design and to evaluate transfer effects and changes in brain activation.Methods: Thirty patients with a-MCI were randomized into MST or education program. At baseline, participants completed clinical and neuropsychological assessments as well as structural and functional magnetic resonance imaging (fMRI). Interventions were administered individually and comprised four sessions, over 2 weeks. MST taught patients to use a three-step process to learn and recall face-name associations. Post-treatment assessment included fMRI, a separate face-name association task, neuropsychological tests, and measures of metamemory. Behavioral (i.e., non-fMRI) measures were repeated after one and 3-months.Results: Participants in the MST condition showed greater improvement on measures of face-name memory, and increased associative strategy use; effects that were accompanied by increased fMRI activation in the left anterior temporal lobe. While all participants reported greater contentment with their everyday memory following intervention, only the MST group reported significant improvements in their memory abilities. There was no clear indication of far-transfer effects to other neuropsychological tests.Conclusion: Results demonstrate that patients with a-MCI not only show stimulus specific benefits of MST, but that they appear capable of transferring training to at least some other cognitive tasks. MST also facilitated the use of brain regions that are involved in face processing, episodic and semantic memory, and social cognition, which are consonant with the cognitive processes engaged by training

High Levels of Diversity Uncovered in a Widespread Nominal Taxon: Continental Phylogeography of the Neotropical Tree Frog

Species distributed across vast continental areas and across major biomes provide unique model systems for studies of biotic diversification, yet also constitute daunting financial, logistic and political challenges for data collection across such regions. The tree frog Dendropsophus minutus (Anura: Hylidae) is a nominal species, continentally distributed in South America, that may represent a complex of multiple species, each with a more limited distribution. To understand the spatial pattern of molecular diversity throughout the range of this species complex, we obtained DNA sequence data from two mitochondrial genes, cytochrome oxidase I (COI) and the 16S rhibosomal gene (16S) for 407 samples of D. minutus and closely related species distributed across eleven countries, effectively comprising the entire range of the group. We performed phylogenetic and spatially explicit phylogeographic analyses to assess the genetic structure of lineages and infer ancestral areas. We found 43 statistically supported, deep mitochondrial lineages, several of which may represent currently unrecognized distinct species. One major clade, containing 25 divergent lineages, includes samples from the type locality of D. minutus. We defined that clade as the D. minutus complex. The remaining lineages together with the D. minutus complex constitute the D. minutus species group. Historical analyses support an Amazonian origin for the D. minutus species group with a subsequent dispersal to eastern Brazil where the D. minutus complex originated. According to our dataset, a total of eight mtDNA lineages have ranges >100,000 km2. One of them occupies an area of almost one million km2 encompassing multiple biomes. Our results, at a spatial scale and resolution unprecedented for a Neotropical vertebrate, confirm that widespread amphibian species occur in lowland South America, yet at the same time a large proportion of cryptic diversity still remains to be discovered