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1.
ACS Sens ; 2021 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-33480678

RESUMO

This work proposed a new sensing strategy for protease detection by converting a homogeneous assay into a surface-tethered electrochemical analysis. Streptavidin (SA), a tetramer protein, was used as the sensing unit based on the SA-biotin coupling chemistry. Caspase-3 was used as the model analyte, and a biotinylated peptide with a sequence of biotin-GDEVDGK-biotin was designed as the substrate. Specifically, the peptide substrate could induce an assembly of SA to form (SA-biotin-GDEVDGK-biotin)n aggregates through SA-biotin interactions, which was confirmed by atomic force microscopy (AFM). The peptide substrate-induced assembly of SA was facilely initiated on an electrode-liquid surface by modification of the electrode with SA. The in situ formation of (SA-biotin-GDEVDGK-biotin)n aggregates created an insulating layer, thus limiting the electron transfer of ferricyanide. Once the peptide substrate was cleaved into two shorter fragments (biotin-GDEVD and GK-biotin) by caspase-3, the resulting products would compete with biotin-GDEVDGK-biotin to bind SA proteins immobilized on the electrode surface and distributed in a solution, thus preventing the in situ formation of (SA-biotin-GDEVDGK-biotin)n assemblies. With the simple principle of the substrate-induced assembly of SA, a dual-signal amplification was achieved with improved sensitivity. Taking advantage of high sensitivity, simple principle, and easy operation, this method can be augmented to design various surface-tethered biosensors for practical applications.

2.
Q J Exp Psychol (Hove) ; : 1747021820981862, 2020 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-33283640

RESUMO

The effect of the babyface schema includes three typical responses, namely, the preference response, viewing motivation, and attention bias towards infant faces. It has been theorized that these responses are primarily influenced by infants' facial structures. However, recent studies have revealed the moderating role of facial expression, suggesting that the strongest effect of the babyface schema may be related to the neutral facial expression; this hypothesis remains to be tested. In this study, the moderating role of facial expression was assessed in three successive experiments (total N = 402). We used a series of images of the same face with multiple expression-standardized images of infants and adults to control for facial structure. The results indicated that the effect sizes of the babyface schema (i.e., response differences between infants and adults) were different for multiple expressions of the same face. Specifically, the effect sizes of neutral faces were significantly greater than those of happy and sad faces according to the preference response (experiment 1, N = 90), viewing motivation (experiment 2, N = 214), and attentional bias (experiment 3, N = 98). These results empirically confirm that neutral infant facial expressions elicit the strongest effect of the babyface schema under the condition of using adult faces as a comparison baseline and matching multiple expressions of the same face.

3.
PLoS One ; 15(11): e0242203, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33180806

RESUMO

Guided by parental investment theory and social role theory, this study aimed to understand current contradictory results regarding sex differences in response to infant faces by considering the effect of gender role orientation. We recruited 300 adults in China and asked them to complete an Interest in Infants questionnaire and a Bem Sex Role Inventory and then administered a behavioral assessment that used unfamiliar infant faces with varying expressions (laughing, neutral, and crying) as stimuli to gauge three components of motivation towards infants (i.e., liking, representational responding, and evoked responding). The results demonstrated that sex differences emerged only in self-reported interest in infants, but no difference was found between the sexes in terms of their hedonic reactions to infant faces. Furthermore, femininity was found to correlate with preferences for infants in both verbal and visual tests, but significant interactive effects of feminine traits and sex were found only in the behavioral test. The findings indicated that men's responses to infants were influenced more by their feminine traits than were women's responses, potentially explaining the greater extent to which paternal (vs. maternal) investment is facultative.

4.
Nat Struct Mol Biol ; 26(6): 424-432, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31133700

RESUMO

In eukaryotic cells, many introns are constitutively, rather than alternatively, spliced and therefore do not contribute to isoform diversification. It has remained unclear what functional roles such constitutive splicing provides. To explore this issue, we asked how splicing affects the efficiency with which individual pre-messenger RNA transcripts are productively processed across different gene expression levels. We developed a quantitative single-molecule fluorescence in situ hybridization-based method to quantify splicing efficiency at transcription active sites in single cells. We found that both natural and synthetic genes in mouse and human cells exhibited an unexpected 'economy of scale' behavior in which splicing efficiency increased with transcription rate. Correlations between splicing efficiency and spatial proximity to nuclear speckles could explain this counterintuitive behavior. Functionally, economy of scale splicing represents a non-linear filter that amplifies the expression of genes when they are more strongly transcribed. These results indicate that constitutive splicing plays an active functional role in modulating gene expression.


Assuntos
Processamento de RNA , Ativação Transcricional , Animais , Linhagem Celular , Éxons , Humanos , Hibridização in Situ Fluorescente/métodos , Íntrons , Camundongos , Modelos Genéticos , Análise de Célula Única/métodos
5.
Front Psychol ; 8: 85, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28184210

RESUMO

Objective: To determine the influence of adult attachment orientations on infant preference. Methods: We adopted eye-tracking technology to monitor childless college women's eye movements when looking at pairs of faces, including one adult face (man or woman) and one infant face, with three different expressions (happy, sadness, and neutral). The participants (N = 150; 84% Han ethnicity) were aged 18-29 years (M = 19.22, SD = 1.72). A random intercepts multilevel linear regression analysis was used to assess the unique contribution of attachment avoidance, determined using the Experiences in Close Relationships scale, to preference for infant faces. Results: Women with higher attachment avoidance showed less infant preference, as shown by less sustained overt attentional bias to the infant face than the adult face based on fixation time and count. Conclusion: Adult attachment might be related to infant preference according to eye movement indices. Women with higher attachment avoidance may lack attentional preference for infant faces. The findings may aid the treatment and remediation of the interactions between children and mothers with insecure attachment.

6.
Front Psychol ; 7: 1237, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27582724

RESUMO

This study examined the association between infant facial expressions and parental motivation as well as the interaction between attachment state and expressions. Two-hundred eighteen childless adults (M age = 19.22, 118 males, 100 females) were recruited. Participants completed the Chinese version of the State Adult Attachment Measure and the E-prime test, which comprised three components (a) liking, the specific hedonic experience in reaction to laughing, neutral, and crying infant faces; (b) representational responding, actively seeking infant faces with specific expressions; and (c) evoked responding, actively retaining images of three different infant facial expressions. While the first component refers to the "liking" of infants, the second and third components entail the "wanting" of an infant. Random intercepts multilevel models with emotion nested within participants revealed a significant interaction between secure attachment state and emotion on both liking and representational response. A hierarchical regression analysis was conducted to examine the unique contributions of secure attachment state. Findings demonstrated that, after controlling for sex, anxious, and avoidant, secure attachment state positively predicted parental motivations (liking and wanting) in the neutral and crying conditions, but not the laughing condition. These findings demonstrate the significant role of secure attachment state in parental motivation, specifically when infants display uncertain and negative emotions.

7.
Int J Soc Psychiatry ; 61(6): 569-76, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25550327

RESUMO

AIMS: The social causation hypothesis suggests that the stress in connection with a depressing social position results in the development of mental disorders. This study examines the psychological mechanisms underlying the link between family socioeconomic status (SES) and social anxiety in Chinese emerging adults. METHODS: A self-administered questionnaire was given to a representative sample (N = 717) of undergraduate students (17-23 years old) at three universities in China. Correlational and structural equation modeling analyses were employed to test the hypothesized three-path effect of self-esteem and fear of negative evaluation (FNE) as mediators between family SES and social anxiety. RESULTS: Findings suggest the following: (1) the emerging adults belonging to families with low SES are at an increased risk of social anxiety, and (2) lower family SES caused lower self-esteem, which, in turn, serves to enhance the levels of FNE, thereby increasing social anxiety. CONCLUSION: In addressing the prevention and treatment of social anxiety, we conclude that preventive efforts toward improving self-esteem may help reduce social anxiety in individuals with low family SES.


Assuntos
Transtornos Fóbicos/psicologia , Autoimagem , Adolescente , China/epidemiologia , Família , Medo , Feminino , Humanos , Masculino , Transtornos Fóbicos/epidemiologia , Transtornos Fóbicos/etiologia , Classe Social , Inquéritos e Questionários , Adulto Jovem
8.
Nucleic Acids Res ; 40(13): 6187-98, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22434886

RESUMO

Rapid and processive leading-strand DNA synthesis in the bacteriophage T4 system requires functional coupling between the helicase and the holoenzyme, consisting of the polymerase and trimeric clamp loaded by the clamp loader. We investigated the mechanism of this coupling on a DNA hairpin substrate manipulated by a magnetic trap. In stark contrast to the isolated enzymes, the coupled system synthesized DNA at the maximum rate without exhibiting fork regression or pauses. DNA synthesis and unwinding activities were coupled at low forces, but became uncoupled displaying separate activities at high forces or low dNTP concentration. We propose a collaborative model in which the helicase releases the fork regression pressure on the holoenzyme allowing it to adopt a processive polymerization conformation and the holoenzyme destabilizes the first few base pairs of the fork thereby increasing the efficiency of helicase unwinding. The model implies that both enzymes are localized at the fork, but does not require a specific interaction between them. The model quantitatively reproduces homologous and heterologous coupling results under various experimental conditions.


Assuntos
DNA Helicases/metabolismo , DNA Polimerase Dirigida por DNA/metabolismo , DNA/biossíntese , Proteínas Virais/metabolismo , Fagos Bacilares/enzimologia , Bacteriófago T4/enzimologia , Replicação do DNA , Proteínas de Ligação a DNA/metabolismo , Exodesoxirribonucleases/metabolismo , Holoenzimas/metabolismo , Complexos Multienzimáticos/metabolismo
9.
Nucleic Acids Res ; 40(13): 6174-86, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22434889

RESUMO

Replicative holoenzymes exhibit rapid and processive primer extension DNA synthesis, but inefficient strand displacement DNA synthesis. We investigated the bacteriophage T4 and T7 holoenzymes primer extension activity and strand displacement activity on a DNA hairpin substrate manipulated by a magnetic trap. Holoenzyme primer extension activity is moderately hindered by the applied force. In contrast, the strand displacement activity is strongly stimulated by the applied force; DNA polymerization is favoured at high force, while a processive exonuclease activity is triggered at low force. We propose that the DNA fork upstream of the holoenzyme generates a regression pressure which inhibits the polymerization-driven forward motion of the holoenzyme. The inhibition is generated by the distortion of the template strand within the polymerization active site thereby shifting the equilibrium to a DNA-protein exonuclease conformation. We conclude that stalling of the holoenzyme induced by the fork regression pressure is the basis for the inefficient strand displacement synthesis characteristic of replicative polymerases. The resulting processive exonuclease activity may be relevant in replisome disassembly to reset a stalled replication fork to a symmetrical situation. Our findings offer interesting applications for single-molecule DNA sequencing.


Assuntos
DNA Polimerase Dirigida por DNA/metabolismo , DNA/biossíntese , Proteínas Virais/metabolismo , DNA/metabolismo , Replicação do DNA , Holoenzimas/metabolismo , Cinética , Análise de Sequência de DNA
10.
Nat Methods ; 9(4): 367-72, 2012 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-22406857

RESUMO

High-throughput, low-cost DNA sequencing has emerged as one of the challenges of the postgenomic era. Here we present the proof of concept for a single-molecule platform that allows DNA identification and sequencing. In contrast to most present methods, our scheme is not based on the detection of the fluorescent nucleotides but on DNA hairpin length. By pulling on magnetic beads tethered by a DNA hairpin to the surface, the molecule can be unzipped. In this open state it can hybridize with complementary oligonucleotides, which transiently block the hairpin rezipping when the pulling force is reduced. By measuring from the surface to the bead of a blocked hairpin, one can determine the position of the hybrid along the molecule with nearly single-base precision. Our approach can be used to identify a DNA fragment of known sequence in a mix of various fragments and to sequence an unknown DNA fragment by hybridization or ligation.


Assuntos
DNA/genética , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Sequência de Bases , DNA/química , DNA/metabolismo , DNA Ligases/metabolismo , Sequência Rica em GC , Sequenciamento de Nucleotídeos em Larga Escala/instrumentação , Magnetismo , Conformação de Ácido Nucleico , Hibridização de Ácido Nucleico , Moldes Genéticos
11.
PLoS One ; 7(2): e31845, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22359636

RESUMO

Among chromatin remodeling factors, the ISWI family displays a nucleosome-enhanced ATPase activity coupled to DNA translocation. While these enzymes are known to bind to DNA, their activity has not been fully characterized. Here we use TEM imaging and single molecule manipulation to investigate the interaction between DNA and yeast Isw1a. We show that Isw1a displays a highly cooperative ATP-independent binding to and bridging between DNA segments. Under appropriate tension, rare single nucleation events can sometimes be observed and loop DNA with a regular step. These nucleation events are often followed by binding of successive complexes bridging between nearby DNA segments in a zipper-like fashion, as confirmed by TEM observations. On nucleosomal substrates, we show that the specific ATP-dependent remodeling activity occurs in the context of cooperative Isw1a complexes bridging extranucleosomal DNA. Our results are interpreted in the context of the recently published partial structure of Isw1a and support its acting as a "protein ruler" (with possibly more than one tick).


Assuntos
Adenosina Trifosfatases/metabolismo , DNA Fúngico/metabolismo , Proteínas de Ligação a DNA/metabolismo , Nucleossomos/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/enzimologia , Adenosina Trifosfatases/ultraestrutura , Trifosfato de Adenosina/metabolismo , DNA Fúngico/ultraestrutura , Proteínas de Ligação a DNA/ultraestrutura , Microscopia Eletrônica de Transmissão , Ligação Proteica , Saccharomyces cerevisiae/ultraestrutura , Proteínas de Saccharomyces cerevisiae/ultraestrutura , Especificidade por Substrato
12.
Methods Enzymol ; 475: 297-320, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-20627163

RESUMO

Single-molecule manipulation methods have opened a new vista on the study of molecular motors. Here we describe the use of magnetic traps for the investigation of the mechanism of DNA based motors, in particular helicases and translocases.


Assuntos
DNA Helicases/química , Magnetismo , Torção Mecânica , DNA Helicases/metabolismo , Magnetismo/instrumentação , Magnetismo/métodos , Translocases Mitocondriais de ADP e ATP/química , Translocases Mitocondriais de ADP e ATP/metabolismo
13.
Curr Opin Struct Biol ; 19(5): 615-22, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19783425

RESUMO

Magnetic traps provide a simple technique to pull and twist a variety of biomolecules and monitor the resulting change in extension. They have been used with great success to investigate the interaction of stretched and supercoiled DNA and DNA fibers (e.g. chromatin) with a great variety of enzymes. In this small review we will address their recent use in the study of topoisomerases, gyrase, DNA translocases and various structural proteins.


Assuntos
Bioquímica/métodos , DNA de Cadeia Simples/química , DNA de Cadeia Simples/metabolismo , Magnetismo , Proteínas/química , Proteínas/metabolismo , Animais , Enzimas/metabolismo , Humanos , Ligação Proteica
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