Synthesis of Trifluoromethyl Ketones via Tandem Claisen Condensation and Retro-Claisen C–C Bond-Cleavage Reaction

A highly efficient, operationally simple approach to trifluoromethyl ketones has been developed that builds on the use of a tandem process involving Claisen condensation and retro-Claisen C–C bond cleavage reaction. Enolizable alkyl phenyl ketones were found to react readily with ethyl trifuoroacetate under the promotion of NaH to afford trifluoroacetic ester/ketone exchange products, trifluoromethyl ketones, which were quite different from the general Claisen condensation products, β-diketones. This procedure uses readily available starting materials and can be extended to the preparation of perfluoroalkyl ketones in excellent yield

High-Accuracy Peptide Mass Fingerprinting Using Peak Intensity Data with Machine Learning

For MALDI-TOF mass spectrometry, we show that the intensity of a peptide–ion peak is directly correlated with its sequence, with the residues M, H, P, R, and L having the most substantial effect on ionization. We developed a machine learning approach that exploits this relationship to significantly improve peptide mass fingerprint (PMF) accuracy based on training data sets from both true-positive and false-positive PMF searches. The model’s cross-validated accuracy in distinguishing real versus false-positive database search results is 91%, rivaling the accuracy of MS/MS-based protein identification

Hydrothermal Derived LaOF:Ln³⁺ (Ln = Eu, Tb, Sm, Dy, Tm, and/or Ho) Nanocrystals with Multicolor-Tunable Emission Properties

A series of LaOF:Ln³⁺ (Ln = Eu, Tb, Sm, Dy, Tm, and/or Ho) nanocrystals with good dispersion have been successfully prepared by the hydrothermal method followed a heat-treatment process. Under ultraviolet radiation and low-voltage electron beam excitation, the LaOF:Ln³⁺ nanocrystals show the characteristic f-f emissions of Ln³⁺ (Ln = Eu, Tb, Sm, Dy, Tm, or Ho) and give red, blue-green, orange, yellow, blue, and green emission, respectively. Moreover, there exists simultaneous luminescence of Tb³⁺, Eu³⁺, Sm³⁺, Dy³⁺, Tm³⁺, or Ho³⁺ individually when codoping them in the single-phase LaOF host (for example, LaOF:Tb³⁺, Eu³⁺/Sm³⁺; LaOF:Tm³⁺, Dy³⁺/Ho³⁺; LaOF:Tm³⁺, Ho³⁺, Eu³⁺ systems), which is beneficial to tune the emission colors. Under low-voltage electron beam excitation, a variety of colors can be efficiently adjusted by varying the doping ions and the doping concentration, making these materials have potential applications in field-emission display devices. More importantly, the energy transfer from Tm³⁺ to Ho³⁺ in the LaOF:Tm³⁺, Ho³⁺ samples under UV excitation was first investigated and has been demonstrated to be a resonant type via a quadrupole-quadrupole mechanism. The critical distance (<i>R</i>_Tm–Ho) is calculated to be 28.4 Å. In addition, the LaOF:Tb³⁺ and LaOF:Tm³⁺ phosphors exhibit green and blue luminescence with better chromaticity coordinates, color purity, and higher intensity compared with the commercial green phosphor ZnO:Zn and blue phosphor Y₂SiO₅:Ce³⁺ to some extent under low-voltage electron beam excitation

Luminescence and Energy Transfer Properties of Ca₂Ba₃(PO₄)₃Cl and Ca₂Ba₃(PO₄)₃Cl:A (A = Eu²⁺/Ce³⁺/Dy³⁺/Tb³⁺) under UV and Low-Voltage Electron Beam Excitation

Pure Ca₂Ba₃(PO₄)₃Cl and rare earth ion (Eu²⁺/Ce³⁺/Dy³⁺/Tb³⁺) doped Ca₂Ba₃(PO₄)₃Cl phosphors with the apatite structure have been prepared via a Pechini-type sol–gel process. X-ray diffraction (XRD) and structure refinement, photoluminescence (PL) spectra, cathodoluminescence (CL) spectra, absolute quantum yield, as well as lifetimes were utilized to characterize samples. Under UV light excitation, the undoped Ca₂Ba₃(PO₄)₃Cl sample shows broad band photoluminescence centered near 480 nm after being reduced due to the defect structure. Eu²⁺ and Ce³⁺ ion doped Ca₂Ba₃(PO₄)₃Cl samples also show broad 5d → 4f transitions with cyan and blue colors and higher quantum yields (72% for Ca₂Ba₃(PO₄)₃Cl:0.04Eu²⁺; 67% for Ca₂Ba₃(PO₄)₃Cl:0.016Ce³⁺). For Dy³⁺ and Tb³⁺ doped Ca₂Ba₃(PO₄)₃Cl samples, they give strong line emissions coming from 4f → 4f transitions. Moreover, the Ce³⁺ ion can transfer its energy to the Tb³⁺ ion in the Ca₂Ba₃(PO₄)₃Cl host, and the energy transfer mechanism has been demonstrated to be a resonant type, via a dipole–quadrupole interaction. However, under the low voltage electron beam excitation, Tb³⁺ ion doped Ca₂Ba₃(PO₄)₃Cl samples present different luminescence properties compared with their PL spectra, which is ascribed to the different excitation mechanism. On the basis of the good PL and CL properties of the Ca₂Ba₃(PO₄)₃Cl:A (A = Ce³⁺/Eu²⁺/Tb³⁺/Dy³⁺), Ca₂Ba₃(PO₄)₃Cl might be promising for application in solid state lighting and field-emission displays

Labeling Lysosomes and Tracking Lysosome-Dependent Apoptosis with a Cell-Permeable Activity-Based Probe

In this study, we describe a new strategy for labeling and tracking lysosomes with a cell-permeable fluorescent activity-based probe (CpFABP) that is covalently bound to select lysosomal proteins. Colocalization studies that utilized LysoTracker probes as standard lysosomal markers demonstrated that our novel probe is effective in specifically labeling lysosomes in various kinds of live cells. Furthermore, our studies revealed that this probe has the ability to label fixed cells, permeabilized cells, and NH₄Cl-treated cells, unlike LysoTracker probes, which show ineffective labeling under the same conditions. Remarkably, when applied to monitor the process of lysosome-dependent apoptosis, our probe not only displayed the expected release of lysosomal cathepsins from lysosomes into the cytosol but also revealed additional information about the location of the cathepsins during apoptosis, which is undetectable by other chemical lysosome markers. These results suggest a wide array of promising applications for our probe and provide useful guidelines for its use as a lysosome marker in lysosome-related studies

Blue Emitting Ca₈La₂(PO₄)₆O₂:Ce³⁺/Eu²⁺ Phosphors with High Color Purity and Brightness for White LED: Soft-Chemical Synthesis, Luminescence, and Energy Transfer Properties

Ce³⁺ and/or Eu²⁺ activated Ca₈La₂(PO₄)₆O₂ (CLPA) oxyapatite blue phosphors have been prepared via a Pechini-type sol–gel process. X-ray diffraction (XRD), photoluminescence (PL) spectra, absolute quantum yield, as well as lifetimes were utilized to characterize samples. The emission of Ce³⁺ and Eu²⁺ ions at different lattice sites has been identified and discussed. The CLPA:0.04Ce³⁺ phosphor exhibits bright blue emission with higher quantum yield (67%) and excellent CIE coordinates (<i>x</i> = 0.160, <i>y</i> = 0.115) under UV excitation, and the CLPA:0.05Eu²⁺ phosphor also exhibits blue emission with CIE coordinates (0.187, 0.164). The energy transfer from Ce³⁺ to Eu²⁺ in CLPA:Ce³⁺/Eu²⁺ phosphors has been validated and demonstrated to be a resonant type via a dipole–dipole mechanism. The critical distance (<i>R</i>_c) of Ce³⁺ to Eu²⁺ ions in CLPA was calculated (by the spectral overlap method) to be 26.67 Å. The quantum yields of Ce³⁺ and Eu²⁺ coactivated CLPA phosphors are enhanced compared with that of Eu²⁺ activated samples due to energy transfer. The CIE coordinates of CLPA:0.04Ce³⁺, 0.02Eu²⁺ are (0.179, 0.169). The corresponding luminescence and energy transfer mechanisms have been proposed in detail. These blue phosphors might be promising for use in pc-white LEDs

Spontaneous, local diastolic subsarcolemmal calcium releases in single, isolated guinea-pig sinoatrial nodal cells

<div><p>Uptake and release calcium from the sarcoplasmic reticulum (SR) (dubbed “calcium clock”), in the form of spontaneous, rhythmic, local diastolic calcium releases (LCRs), together with voltage-sensitive ion channels (membrane clock) form a coupled system that regulates the action potential (AP) firing rate. LCRs activate Sodium/Calcium exchanger (NCX) that accelerates diastolic depolarization and thus participating in regulation of the time at which the next AP will occur. Previous studies in rabbit SA node cells (SANC) demonstrated that the basal AP cycle length (APCL) is tightly coupled to the basal LCR period (time from the prior AP-induced Ca²⁺ transient to the diastolic LCR occurrence), and that this coupling is further modulated by autonomic receptor stimulation. Although spontaneous LCRs during diastolic depolarization have been reported in SANC of various species (rabbit, cat, mouse, toad), prior studies have failed to detect LCRs in spontaneously beating SANC of guinea-pig, a species that has been traditionally used in studies of cardiac pacemaker cell function. We performed a detailed investigation of whether guinea-pig SANC generate LCRs and whether they play a similar key role in regulation of the AP firing rate. We used two different approaches, 2D high-speed camera and classical line-scan confocal imaging. Positioning the scan-line beneath sarcolemma, parallel to the long axis of the cell, we found that rhythmically beating guinea-pig SANC do, indeed, generate spontaneous, diastolic LCRs beneath the surface membrane. The average key LCR characteristics measured in confocal images in guinea-pig SANC were comparable to rabbit SANC, both in the basal state and in the presence of β-adrenergic receptor stimulation. Moreover, the relationship between the LCR period and APCL was subtended by the same linear function. Thus, LCRs in guinea-pig SANC contribute to the diastolic depolarization and APCL regulation. Our findings indicate that coupled-clock system regulation of APCL is a general, species-independent, mechanism of pacemaker cell normal automaticity. Lack of LCRs in prior studies is likely explained by technical issues, as individual LCRs are small stochastic events occurring mainly near the cell border.</p></div

Both GP and R single rhythmically beating SANC generate spontaneous diastolic LCRs beneath sarcolemma under the basal conditions.

<p>Representative examples of confocal line scan images of LCRs (marked with asterisks) and AP-induced Ca²⁺ transient recorded in SANC of GP (A) and R (B). (C) Schematic illustration of the correct scan-line orientation along the cell border. (D) Definition of the LCR period and AP cycle length (APCL).</p

AP cycle length (APCL) in both GP and R single rhythmically beating SANC is tightly coupled to LCR period under the basal conditions.

<p>(A) Histogram of distributions of all individual APCLs, and (B) Individual LCRs periods in GP (91, LCRs from 13 cells) and R SANC (422 LCRs from 31 cells). Insets in (A) and (B) show the average APCL (interval between AP-induced Ca²⁺ transients) and LCR period (the time between the rapid upstroke of the prior AP-triggered Ca²⁺ transient and the onset of a LCR in diastole) in GP (n = 13) and R (n = 31) SANC. (C) Relationship of the average APCL to the average LCR period is subtended by the same linear function in GP SANC (y = 1.2x + 8.3; R² = 1.0; n = 13) and R SANC (y = 1.1x + 27.8; R² = 1.0; n = 31). (D) Average CV of APCL (measured as SD/Mean) in GP and R SANC.</p

Synthesis of (<i>Z</i>)‑α-Trifluoromethyl Alkenyl Triflate: A Scaffold for Diverse Trifluoromethylated Species

An efficient method for the synthesis of (<i>Z</i>)-selective α-trifluoromethyl alkenyl triflates is described. As an important fluorinated building block, it is utilized successfully for the synthesis of various trifluoromethyl derivatives such as diarylethylenes, enynes, alkynes, and benzofurans