Intermediate Levels of Hippocampal Activity Appear Optimal for Associative Memory Formation

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Affinity purification of recombinant human plasminogen activator from transgenic rabbit milk using a novel polyolresponsive monoclonal antibody

Purpose: To develop processes for effective isolation and purification of recombinant human plasminogen activator (rhPA) from transgenic rabbit milk.Methods: Immunoaffinity chromatography was selected and improved by a special polyol-responsive monoclonal antibody (PR-mAb). Alteplase was used as immunogen because of its similarity to rhPA in terms of structure. The PR-mAb was prepared by hybridoma technology and screened by ELISA-elution assay. Screening antibody was performed using rhPA milk in an ELISA-elution assay. The antibody clone C4-PR-mAb was selected for immunoaffinity chromatography. The rhPA was effectively bound to immobilized C4-PR-mAb on the column and was eluted with Tris buffer comprising 0.75 mol/L ammonium sulfate and 40n% propanediol (pH7.9). The rhPA was further purified by passing through Chromdex75 gel filtration column.Results: There were 12 hybridoma strains selected into the polyol responsive mAbs screen step and three hybridoma strains were superior for producing PR-mAbs (C1, C4, C8). The rhPA can be purified from transgenic rabbit milk and maintained a higher thrombolytic activity in vitro by FAPA.Conclusion: The results demonstrate the suitability of the alternative approach used in this study. Using immunoaffinity chromatography and  gel filtration column is feasible and convenient for extracting rhPA from milk, and should be useful for purifying other tPA mutants or other novel recombinant milkderived proteins.Keywords: tPA, Immunoaffinity chromatography, PR-mAb, ELISA-elution, Antibody, Thrombolytic activit

Maternal body fluid lncRNAs serve as biomarkers to diagnose ventricular septal defect: from amniotic fluid to plasma

Background: Maternal body fluids contain abundant cell-free fetal RNAs which have the potential to serve as indicators of fetal development and pathophysiological conditions. In this context, this study aimed to explore the potential diagnostic value of maternal circulating long non-coding RNAs (lncRNAs) in ventricular septal defect (VSD).Methods: The potential of lncRNAs as non-invasive prenatal biomarkers for VSD was evaluated using quantitative polymerase chain reaction (qPCR) and receiver operating characteristic (ROC) curve analysis. The biological processes and regulatory network of these lncRNAs were elucidated through bioinformatics analysis.Results: Three lncRNAs (LINC00598, LINC01551, and GATA3-AS1) were found to be consistent in both maternal plasma and amniotic fluid. These lncRNAs exhibited strong diagnostic performance for VSD, with AUC values of 0.852, 0.957, and 0.864, respectively. The bioinformatics analysis revealed the involvement of these lncRNAs in heart morphogenesis, actin cytoskeleton organization, cell cycle regulation, and protein binding through a competitive endogenous RNA (ceRNA) network at the post-transcriptional level.Conclusion: The cell-free lncRNAs present in the amniotic fluid have the potential to be released into the maternal circulation, making them promising candidates for investigating epigenetic regulation in VSD

The Integrative Effects of Cognitive Reappraisal on Negative Affect: Associated Changes in Secretory Immunoglobulin A, Unpleasantness and ERP Activity

Although the regulatory role of cognitive reappraisal in negative emotional responses is widely recognized, this reappraisal's effect on acute saliva secretory immunoglobulin A (SIgA), as well as the relationships among affective, immunological, and event-related potential (ERP) changes, remains unclear. In this study, we selected only people with low positive coping scores (PCSs) as measured by the Trait Coping Style Questionnaire to avoid confounding by intrinsic coping styles. First, we found that the acute stress of viewing unpleasant pictures consistently decreased SIgA concentration and secretion rate, increased perceptions of unpleasantness and amplitude of late positive potentials (LPPs) between 200–300 ms and 400–1000 ms. After participants used cognitive reappraisal, their SIgA concentration and secretion rate significantly increased and their unpleasantness and LPP amplitudes significantly decreased compared with a control condition. Second, we found a significantly positive correlation between the increases in SIgA and the decreases in unpleasantness and a significantly negative correlation between the increases in SIgA and the increases in LPP across the two groups. This study is the first to demonstrate that cognitive reappraisal reverses the decrease of SIgA. In addition, it revealed strong correlations among affective, SIgA and electrophysiological changes with convergent multilevel evidence

Can Sophie's Choice Be Adequately Captured by Cold Computation of Minimizing Losses? An fMRI Study of Vital Loss Decisions

The vast majority of decision-making research is performed under the assumption of the value maximizing principle. This principle implies that when making decisions, individuals try to optimize outcomes on the basis of cold mathematical equations. However, decisions are emotion-laden rather than cool and analytic when they tap into life-threatening considerations. Using functional magnetic resonance imaging (fMRI), this study investigated the neural mechanisms underlying vital loss decisions. Participants were asked to make a forced choice between two losses across three conditions: both losses are trivial (trivial-trivial), both losses are vital (vital-vital), or one loss is trivial and the other is vital (vital-trivial). Our results revealed that the amygdala was more active and correlated positively with self-reported negative emotion associated with choice during vital-vital loss decisions, when compared to trivial-trivial loss decisions. The rostral anterior cingulate cortex was also more active and correlated positively with self-reported difficulty of choice during vital-vital loss decisions. Compared to the activity observed during trivial-trivial loss decisions, the orbitofrontal cortex and ventral striatum were more active and correlated positively with self-reported positive emotion of choice during vital-trivial loss decisions. Our findings suggest that vital loss decisions involve emotions and cannot be adequately captured by cold computation of minimizing losses. This research will shed light on how people make vital loss decisions

DPHL: A DIA Pan-human Protein Mass Spectrometry Library for Robust Biomarker Discovery

To address the increasing need for detecting and validating protein biomarkers in clinical specimens, mass spectrometry (MS)-based targeted proteomic techniques, including the selected reaction monitoring (SRM), parallel reaction monitoring (PRM), and massively parallel data-independent acquisition (DIA), have been developed. For optimal performance, they require the fragment ion spectra of targeted peptides as prior knowledge. In this report, we describe a MS pipeline and spectral resource to support targeted proteomics studies for human tissue samples. To build the spectral resource, we integrated common open-source MS computational tools to assemble a freely accessible computational workflow based on Docker. We then applied the workflow to generate DPHL, a comprehensive DIA pan-human library, from 1096 data-dependent acquisition (DDA) MS raw files for 16 types of cancer samples. This extensive spectral resource was then applied to a proteomic study of 17 prostate cancer (PCa) patients. Thereafter, PRM validation was applied to a larger study of 57 PCa patients and the differential expression of three proteins in prostate tumor was validated. As a second application, the DPHL spectral resource was applied to a study consisting of plasma samples from 19 diffuse large B cell lymphoma (DLBCL) patients and 18 healthy control subjects. Differentially expressed proteins between DLBCL patients and healthy control subjects were detected by DIA-MS and confirmed by PRM. These data demonstrate that the DPHL supports DIA and PRM MS pipelines for robust protein biomarker discovery. DPHL is freely accessible at https://www.iprox.org/page/project.html?id=IPX0001400000

Photo-induced Structural Dynamics in Transition Metal Dichalcogenides

Ultrafast electron microscope (UEM), a combination of transmission electron microscopy and laser-based pump-probe techniques, facilitates ultrafast imaging, diffraction, and electron-spectroscopy with high spatial resolution. The unique advantages of UEM enable local ultrafast dynamic studies in materials, nano-system, and biology. The performance of UEM, such as its temporal and energy resolutions and coherence, is largely determined by the quality of electron beam. In this thesis, the beam dynamics in our UEM with a thermionic gun was studied. The influence of cathode geometry and Wehnelt bias voltage on the electron pulse dynamics is determined through experiments and finite element simulations. A guard ring cathode can effectively address the problem of shank-emitted electrons in traditional truncated tip geometries, allowing UEM operation at minimum Wehnelt bias and improving the temporal resolution under realistic conditions. A sub-ps temporal resolution can be reached with few electrons in one pulse. Compared to the 300 fs laser pulse width, the temporal duration of the electron pulse is nevertheless elongated during the propagation in the UEM column. The simulations show that the initial energy spread and the angular distribution from the photoemission process are the dominant factors in this temporal dispersion. Utilizing our UEM, the structural dynamics including photo-induced phase transitions and coherent phonon excitation were studied in two transition metal dichalcogenides (TMDs), 1T-TaSe2 and Td-WTe2. 1T-TaSe2 is a room temperature commensurate charge density wave (C-CDW) material. The C-CDW phase undergoes a phase transition to an incommensurate charge density wave (IC-CDW) at 473 K featured by a rotation of the superstructure. Under photoexcitation, the C-CDW in 1T-TaSe2 can be suppressed within sub-ps time scale. A recovery time-constant of ~0.7 ps is observed for the commensurate periodic lattice distortion (PLD) at a pump fluence insufficient to drive a phase transition into the IC-CDW phase. At higher pump fluence, sufficient to drive nucleation of the IC-CDW phase, there is a ~1 ps delay between the extinction of the C-CDW phase and the onset for formation of the IC-CDW phase. Within the ~1 ps, a transient unreconstructed state may exist. The ~1 ps delay time for the nucleation of the IC-CDW phase implies that a phononic thermalization is involved in the decay of this highly perturbed photoinduced transient state. During the nucleation of the IC-CDW phase, a face-centered cubic (FCC) like stacking order is observed already at ~4 ps after photoexcitation. Such rapid stacking order formation indicates that the nucleation of the IC-CDW phase in the adjacent layers is not independent but coupled together. We can infer that the nucleation of the IC-CDW is inherently 3-dimensional (3D). The highly 3D feature of CDW in 1T-TaSe2 indicates a strong interlayer interaction that establish long range out-of-plane stacking order. Both in 1T-TaSe2 and Td-WTe2, a coherent shear phonon is observed by photoexcitation. In 1T-TaSe2, the coherent shear mode is along the stacking direction of the C-CDW phase. We analyze the launching mechanism in terms of hot/cold spots on the Se-sublattice that result from the rapid melting of the PLD. During the melting, a difference in Se-phonon amplitudes results in shear forces between the layers. For a perfect trigonal stacking, the force will be compensated. However, there always remain uncompensated restoring forces in stacking-order direction because of the domain structure in out-of-plane direction. The excitation of a coherent shear phonon is even stronger in Td-WTe2. The shear direction is along the b axis where there is a stacking displacement for the adjacent layers. In Td-WTe2, a photo-induced phase transition from orthorhombic Td to orthorhombic T* phase is observed which involves a stacking order change in the out-of-plane direction by a layer shear displacement along the b axis direction. Upon photoexcitation with pump fluence higher than a critical value, the change in interlayer potential results in the formation of a new metastable phase with a ~4 ps time constant. The shear displacement of the adjacent layers increases linearly with the increase of pump fluence and stabilize at ~ 8 pm when the pump fluence is higher than ~2 mJ/cm2. The photo-induced phase transition in Td-WTe2 can be influenced by local defect structures. In a ripple defect rich sample, a new phase transition from orthorhombic T* to monoclinic T’ phase will occur following the Td to T* phase transition. It can be inferred that strain fields in the sample can modulate the photo-induced phase stability. This effect has potential application in strain engineering of 2 dimensional TMDs. The observed photo-induced phase transition and coherent shear phonon in 1T-TaSe2 and Td-WTe2, demonstrate the importance of inter-layer interaction in TMDs.

Photo-induced Structural Dynamics in Transition Metal Dichalcogenides

Ultrafast electron microscope (UEM), a combination of transmission electron microscopy and laser-based pump-probe techniques, facilitates ultrafast imaging, diffraction, and electron-spectroscopy with high spatial resolution. The unique advantages of UEM enable local ultrafast dynamic studies in materials, nano-system, and biology. The performance of UEM, such as its temporal and energy resolutions and coherence, is largely determined by the quality of electron beam. In this thesis, the beam dynamics in our UEM with a thermionic gun was studied. The influence of cathode geometry and Wehnelt bias voltage on the electron pulse dynamics is determined through experiments and finite element simulations. A guard ring cathode can effectively address the problem of shank-emitted electrons in traditional truncated tip geometries, allowing UEM operation at minimum Wehnelt bias and improving the temporal resolution under realistic conditions. A sub-ps temporal resolution can be reached with few electrons in one pulse. Compared to the 300 fs laser pulse width, the temporal duration of the electron pulse is nevertheless elongated during the propagation in the UEM column. The simulations show that the initial energy spread and the angular distribution from the photoemission process are the dominant factors in this temporal dispersion. Utilizing our UEM, the structural dynamics including photo-induced phase transitions and coherent phonon excitation were studied in two transition metal dichalcogenides (TMDs), 1T-TaSe2 and Td-WTe2. 1T-TaSe2 is a room temperature commensurate charge density wave (C-CDW) material. The C-CDW phase undergoes a phase transition to an incommensurate charge density wave (IC-CDW) at 473 K featured by a rotation of the superstructure. Under photoexcitation, the C-CDW in 1T-TaSe2 can be suppressed within sub-ps time scale. A recovery time-constant of ~0.7 ps is observed for the commensurate periodic lattice distortion (PLD) at a pump fluence insufficient to drive a phase transition into the IC-CDW phase. At higher pump fluence, sufficient to drive nucleation of the IC-CDW phase, there is a ~1 ps delay between the extinction of the C-CDW phase and the onset for formation of the IC-CDW phase. Within the ~1 ps, a transient unreconstructed state may exist. The ~1 ps delay time for the nucleation of the IC-CDW phase implies that a phononic thermalization is involved in the decay of this highly perturbed photoinduced transient state. During the nucleation of the IC-CDW phase, a face-centered cubic (FCC) like stacking order is observed already at ~4 ps after photoexcitation. Such rapid stacking order formation indicates that the nucleation of the IC-CDW phase in the adjacent layers is not independent but coupled together. We can infer that the nucleation of the IC-CDW is inherently 3-dimensional (3D). The highly 3D feature of CDW in 1T-TaSe2 indicates a strong interlayer interaction that establish long range out-of-plane stacking order. Both in 1T-TaSe2 and Td-WTe2, a coherent shear phonon is observed by photoexcitation. In 1T-TaSe2, the coherent shear mode is along the stacking direction of the C-CDW phase. We analyze the launching mechanism in terms of hot/cold spots on the Se-sublattice that result from the rapid melting of the PLD. During the melting, a difference in Se-phonon amplitudes results in shear forces between the layers. For a perfect trigonal stacking, the force will be compensated. However, there always remain uncompensated restoring forces in stacking-order direction because of the domain structure in out-of-plane direction. The excitation of a coherent shear phonon is even stronger in Td-WTe2. The shear direction is along the b axis where there is a stacking displacement for the adjacent layers. In Td-WTe2, a photo-induced phase transition from orthorhombic Td to orthorhombic T* phase is observed which involves a stacking order change in the out-of-plane direction by a layer shear displacement along the b axis direction. Upon photoexcitation with pump fluence higher than a critical value, the change in interlayer potential results in the formation of a new metastable phase with a ~4 ps time constant. The shear displacement of the adjacent layers increases linearly with the increase of pump fluence and stabilize at ~ 8 pm when the pump fluence is higher than ~2 mJ/cm2. The photo-induced phase transition in Td-WTe2 can be influenced by local defect structures. In a ripple defect rich sample, a new phase transition from orthorhombic T* to monoclinic T’ phase will occur following the Td to T* phase transition. It can be inferred that strain fields in the sample can modulate the photo-induced phase stability. This effect has potential application in strain engineering of 2 dimensional TMDs. The observed photo-induced phase transition and coherent shear phonon in 1T-TaSe2 and Td-WTe2, demonstrate the importance of inter-layer interaction in TMDs.

Manipulation of Stacking Order in Td-WTe2 by Ultrafast Optical Excitation

Subtle changes in stacking order of layered transition metal dichalcogenides may have profound influence on the electronic and optical properties. The intriguing electronic properties of Td-WTe2 can be traced to the break of inversion symmetry resulting from the ground-state stacking sequence. Strategies for perturbation of the stacking order are actively pursued for intentional tuning of material properties, where optical excitation is of specific interest since it holds the potential for integration of ultrafast switches in future device designs. Here we investigate the structural response in Td-WTe2 following ultrafast photoexcitation by time-resolved electron diffraction. A 0.23 THz shear phonon, involving layer displacement along the b axis, was excited by a 515 nm laser pulse. Pump fluences in excess of a threshold of similar to 1 mJ/cm(2) result in formation, with an similar to 5 ps time constant, of a new stacking order by layer displacement along the b axis in the direction toward the centrosymmetric 1T* phase. The shear displacement of the layers increases with pump fluence until saturation at similar to 8 pm. We demonstrate that the excitation of the shear phonon and the stabilization of the metastable phase are decoupled when using an optical pump as evidenced by observation of a transition also in samples with a pinned shear phonon. The results are compared to dynamic first-principles simulations and the transition is interpreted in terms of a mechanism where transient local disorder is prominent before settling at the atomic positions of the metastable phase. This interpretation is corroborated by results from diffuse scattering. The correlation between excitation of intralayer vibrations and interlayer interaction demonstrates the importance of including both short- and long-range interactions in an accurate description of how optical fields can be employed to manipulate the stacking order in 2-dimensional transition metal dichalcogenides