Functional Covalent Organic Framework (COF) Nanoparticles for Biomimic Mineralization and Bacteria Inhabitation.

Biomimic mineralization of hard tissues with hierarchical structures is a challenging task, while designing multifunctional materials possessing both the ability of biomimic mineralization and drug delivery is even more difficult. Herein, inspired by the multilevel structure and mineralization ability of amelogenin, a novel carboxyl-functionalized covalent organic framework (COF) nanosphere material was designed and synthesized, which exhibited a significant biomimetic remineralization ability as demonstrated on SiO2 glass, Ti6Al4V, and an acid-etched enamel surface. Furthermore, the nanoporous structure also enables the COF nanospheres to serve as a drug delivery system for the controlled release of antibacterial drugs. This work provides a promising strategy for the design of multifunctional biomimic materials.

Epithelial TIPE1 Protein Guards against Colitis by Inhibiting TNF-α-Mediated Inflammation.

Intestinal epithelial cells (IECs) at the internal/external interface orchestrate the mucosal immune response, and IEC dysfunction has been linked to multiple inflammatory diseases, including inflammatory bowel disease. In this study, we found that a member of the TNF-α-induced protein 8 (TNFAIP8 or TIPE) family called TIPE1 is indispensable for maintaining epithelial cell barrier integrity and homeostasis under inflammatory conditions. TIPE1-deficient mice, or chimeric mice that were deficient in TIPE1 in their nonhematopoietic cells, were more sensitive to dextran sulfate sodium-induced experimental colitis; however, TIPE1 deficiency had no impact on the development of inflammation-associated and sporadic colorectal cancers. Mechanistically, TIPE1 prevented experimental colitis through modulation of TNF-α-dependent inflammatory response in IECs. Importantly, genetic deletion of both TIPE1 and its related protein TNFAIP8 in mice led to the development of spontaneous chronic colitis, indicating that both of these two TIPE family members play crucial roles in maintaining intestinal homeostasis. Collectively, our findings highlight an important mechanism by which TIPE family proteins maintain intestinal homeostasis and prevent inflammatory disorders in the gut.

Spatial Well-defined Bimetallic Two-Dimensional Polymers with Single-Layer Thickness for Electrocatalytic Oxygen Evolution Reaction.

Innovative bimetallic materials provide more possibilities for further improving the performance of oxygen evolution reaction (OER) electrocatalysts. However, it is still a great challenge to rationally design bimetallic catalysts because there is not a practical way to decouple the factors influencing the intrinsic activity of active sites from others, thus hindering in-depth understanding of the mechanism. Herein, we provide a rational design of bimetallic Ni, Co two-dimensional polymer model OER catalyst. The well-defined architecture, identical density of active sites and monolayer characteristic allow us to decouple the intrinsic activity of active sites from other factors. The results confirmed that the relative position and local coordination environment has significant effect on the synergistic effect of the bimetallic centres. The highest electrocatalytic activity with the turnover frequency value up to 26.19 s-1 was achieved at the overpotential of 500 mV.

Enrichment of short-chain organic acids transferred to submicron sea spray aerosols.

Organic acids, considered to be a substantial component of the marine carbon cycle, can enter the atmosphere through sea spray aerosol (SSA) and further affect the climate. Despite their importance, the distribution and mixing state of organic acids in SSA over the marine boundary layer are poorly understood and therefore need more investigation. Here, we have used ion chromatography (IC) in anion mode to measure short-chain organic acids concentrations in SSA collected throughout a custom-made SSA simulation chamber. The enrichment behavior and morphology of monocarboxylic acids (MAs, C1-8) and dicarboxylic acids (DAs) in submicron SSA were studied in seawater. We found that with MAs addition, the number concentration and mass concentration of SSA particles decreased gradually for C5-8 MAs, whereas they weakly varied with DAs addition due to the fact that carboxyl groups at both ends of DAs increased the surface tension of seawater. Moreover, the target compounds in submicron SSA displayed a surface activity-dependent enrichment behavior, where seawater with stronger surface activity, such as that containing MAs with >5 carbons, was more enriched in SSA in comparison to seawater with weaker surface activity. MAs with chain length <5 carbons were slightly enriched in SSA, whereas the enrichment factor (EF) of C5-8 MAs further increased with increasing chain length. These findings are of utmost importance in further understanding and quantifying the contribution of organic matter to SSA, which is crucial for assessing the atmosphere feedback of the marine carbon cycle. MAIN FINDING OF THE WORK: Surface tension of seawater is the key factor affecting the enrichment of short-chain organic acids in SSA.

Single Molecule Level and Label-Free Determination of Multibiomarkers with an Organic Field-Effect Transistor Platform in Early Cancer Diagnosis.

The single molecule level determination with a transistor (SiMoT) platform has attracted considerable attention in the recognition of various ultralow abundance biomolecules, while complicated labeling and testing processes limit its further applications. Recently, organic field-effect transistor (OFET)-based biosensors are good candidates for constructing an advanced label-free SiMoT platform due to their facile fabrication process, rapid response time, and low sample volume with a wide range of detection. However, the sensitivity of most OFET-based biosensors is in the order of nM and pM, which cannot meet the detection requirements of ultralow abundance protein. Herein, a label-free SiMoT platform is demonstrated by integrating pillar[n]arene as a signal amplifier, and the detection limit can reach 4.75 aM. Besides, by simultaneous determination of α-fetoprotein, carcinoembryonic antigen, and prostate antigen, the proposed multiplexed OFET-based SiMoT platform provides a key step in reliable early cancer diagnosis.

TNFAIP8 protein functions as a tumor suppressor in inflammation-associated colorectal tumorigenesis.

Tumor necrosis factor-α-induced protein 8 (TNFAIP8 or TIPE) is a member of the TNFAIP8 family. While TIPE was broadly considered to be pro-cancerous, its precise roles in carcinogenesis especially those of the intestinal tract are not clear. Here, we show that genetic deletion of TIPE in mice exacerbated chemical-induced colitis and colitis-associated colon cancer. Loss of TIPE exacerbated inflammatory responses and inflammation-associated dysbiosis, leading to the activation of NF-κB and STAT3, and it also accelerated dysplasia, DNA damage and proliferation of intestinal epithelial cells. We further show that colon microbiota were essential for increased tumor growth and progression in Tipe-/- mice. The tumor suppressive function of TIPE originated primarily from the non-hematopoietic compartment. Importantly, TIPE was downregulated in human colorectal cancers, and patients with low levels of Tipe mRNA were associated with reduced survival. These results indicate that TIPE serves as an important modulator of colitis and colitis-associated colon cancer.

Tumor Necrosis Factor-α-Induced Protein 8-Like 2 Fosters Tumor-Associated Microbiota to Promote the Development of Colorectal Cancer.

Although increasing evidence links the gut microbiota with the development of colorectal cancer, the molecular mechanisms for microbiota regulation of tumorigenesis are not fully understood. Here, we found that a member of the TNFα-induced protein 8 (TNFAIP8) family called TIPE2 (TNFAIP8-like 2) was significantly upregulated in murine intestinal tumors and in human colorectal cancer, and colorectal cancer with high expression of Tipe2 mRNA associated with reduced survival time of patients. Consistent with these findings, TIPE2 deficiency significantly inhibited the development of colorectal cancer in mice treated with azoxymethane/dextran sodium sulfate and in Apcmin/+ mice. TIPE2 deficiency attenuated the severity of colitis by successfully resolving and restricting colonic inflammation and protected colonic myeloid cells from death during colitis. Transplantation of TIPE2-deficient bone marrow into wild-type mice successfully dampened the latter's tumorigenic phenotype, indicating a hematopoietic-specific role for TIPE2. Mechanistically, restricting the expansion of Enterobacteriaceae/Escherichia coli (E. coli) decreased intestinal inflammation and reduced the incidence of colonic tumors. Collectively, these data suggest that hematopoietic TIPE2 regulates intestinal antitumor immunity by regulation of gut microbiota. TIPE2 may represent a new therapeutic target for treating colorectal cancer.

Ternary Conductance Switching Realized by a Pillar[5]arene-Functionalized Two-Dimensional Imine Polymer Film.

Nowadays, most manufacturing memory devices are based on materials with electrical bistability (i. e., "0" and "1") in response to an applied electric field. Memory devices with multilevel states are highly desired so as to produce high-density and efficient memory devices. Herein, we report the first multichannel strategy to realize a ternary-state memristor. We make use of the intrinsic sub-nanometer channel of pillar[5]arene and nanometer channel of a two-dimensional imine polymer to construct an active layer with multilevel channels for ternary memory devices. Low threshold voltage, long retention time, clearly distinguishable resistance states, high ON/OFF ratio (OFF/ON1/ON2=1 : 10 : 103 ), and high ternary yield (75 %) were obtained. In addition, the flexible memory device based on 2DPTPAZ+TAPB can maintain its stable ternary memory performance after being bent 500 times. The device also exhibits excellent thermal stability and can tolerate a temperature as high as 300 °C. It is envisioned that the results of this work will open up possibilities for multistate, flexible resistive memories with good thermal stability and low energy consumption, and broaden the application of pillar[n]arene.

Ultrasensitive and Reliable Organic Field-Effect Transistor-Based Biosensors in Early Liver Cancer Diagnosis.

Organic field-effect transistors (OFETs) are considered as one of the cost-effective biosensor devices with rapid detection capabilities and multiparameter responses. However, the functionalization processes on normal organic devices might impact the device performance for its further sensitive and reliable sensing applications. Herein, we develop a novel organic material, 2,6-bis(4-formylphenyl)anthracene (BFPA) for use as the protective and functional layer of OFET-based biosensors, enabling ultrasensitive determination of alpha-fetoprotein (AFP) with femtomolar accuracy in human serum. By monitoring changes of the source-drain current (Ids) and threshold voltage (Vth) electrical signals, the device exhibits improved reliability in detecting AFP biomarkers and is able to differentiate between liver cancer patients and healthy individuals. Featuring label-free determination, shorter analysis time, and lower sample volume, this ultrasensitive and reliable OFET-based biosensor displays numerous advantages over traditional strategies such as enzyme-linked immunosorbent assay and electrochemiluminescence immunoassay, demonstrating that the proposed OFET-based biosensors have broader analytical and clinical applications for early liver cancer diagnosis.

Effect of functional groups on microporous polymer based resistance switching memory devices.

Here, two large-area microporous polymer (MP) films with different substituents were synthesized at the solution/air interface. The on/off ratios of the MP-based memristors differ by an order of magnitude and the turn-on voltages differ by about 0.2 V, which is mainly attributed to the difference in band gap and pore environment of the materials.

The SCFß-TrCP E3 Ubiquitin Ligase Regulates Immune Receptor Signaling by Targeting the Negative Regulatory Protein TIPE2.

TNFAIP8-like 2 (TIPE2) is a negative regulator of immune receptor signaling that maintains immune homeostasis. Dysregulated TIPE2 expression has been observed in several types of human immunological disorders. However, how TIPE2 expression is regulated remains to be determined. We report in this study that the SCFß-TrCP E3 ubiquitin ligase regulates TIPE2 protein abundance by targeting it for ubiquitination and subsequent degradation via the 26S proteasome. Silencing of either cullin-1 or ß-TrCP1 resulted in increased levels of TIPE2 in immune cells. TAK1 phosphorylated the Ser3 in the noncanonical degron motif of TIPE2 to trigger its interaction with ß-TrCP for subsequent ubiquitination and degradation. Importantly, the amount of TIPE2 protein in immune cells determined the strength of TLR 4-induced signaling and downstream gene expression. Thus, our study has uncovered a mechanism by which SCFß-TrCP E3 ubiquitin ligase regulates TLR responses.

An adaptive independence test for microbiome community data.

Advances in sequencing technologies and bioinformatics tools have vastly improved our ability to collect and analyze data from complex microbial communities. A major goal of microbiome studies is to correlate the overall microbiome composition with clinical or environmental variables. La Rosa et al. recently proposed a parametric test for comparing microbiome populations between two or more groups of subjects. However, this method is not applicable for testing the association between the community composition and a continuous variable. Although multivariate nonparametric methods based on permutations are widely used in ecology studies, they lack interpretability and can be inefficient for analyzing microbiome data. We consider the problem of testing for independence between the microbial community composition and a continuous or many-valued variable. By partitioning the range of the variable into a few slices, we formulate the problem as a problem of comparing multiple groups of microbiome samples, with each group indexed by a slice. To model multivariate and over-dispersed count data, we use the Dirichlet-multinomial distribution. We propose an adaptive likelihood-ratio test by learning a good partition or slicing scheme from the data. A dynamic programming algorithm is developed for numerical optimization. We demonstrate the superiority of the proposed test by numerically comparing it with that of La Rosa et al. and other popular approaches on the same topic including PERMANOVA, the distance covariance test, and the microbiome regression-based kernel association test. We further apply it to test the association of gut microbiome with age in three geographically distinct populations and show how the learned partition facilitates differential abundance analysis.

Effect of insect tea on D-galactose-induced oxidation in mice and its mechanisms.

Insect tea is a traditional Chinese drink that contains abundant bioactive substances. In this study, the preventive effect of Insect tea on D-galactose-induced oxidation in mice was studied. The serum, liver, and spleen of mice were measured by biochemical and molecular biological methods, which showed that Insect tea could increase the biochemical indexes of the thymus, brain, heart, liver, spleen, and kidney in mice with induced oxidative damage. Insect tea can increase the levels of SOD (superoxide dismutase), GSH-Px (glutathione peroxidase), and GSH (glutathione) and decrease the levels of MDA (malondialdehyde) in the serum, liver, and spleen of mice with oxidative damage. Pathological observation also confirmed that Insect tea could inhibit oxidative damage of the liver and spleen tissue caused by D-galactose in mice. Further molecular biological experiments also showed that Insect tea could upregulate the mRNA and protein expression of Cu/Zn-SOD (cuprozinc-superoxide dismutase), Mn-SOD (manganese superoxide dismutase), CAT (catalase), HO-1 (heme oxygenase-1), Nrf2 (nuclear factor-erythroid 2 related factor 2), γ-GCS (γ-glutamylcysteine synthetase), and NQO1 (NAD(P)H dehydrogenase [quinone] 1) in the liver and spleen of oxidized mice. Insect tea has a good preventive effect on D-galactose-induced oxidation in mice, and the effect is better than vitamin C, an antioxidant. Insect tea is rich in isochlorogenic acid A, quercetin, rutin, hesperidin, neochlorogenic acid, and cryptochlorogenic acid. The combination of these bioactive substances has good antioxidant effects. Thus, Insect tea is a functional food with a good antioxidant effect that has value for future development and utilization.

Gold nanoparticle-enhanced chemiluminescence detection for CE.

Introducing gold nanoparticles (AuNPs) to the running buffer further improved the sensitivity of luminol-H(2)O(2) chemiluminescence (CL) detection for CE. This has led to the development of sensitive CE-CL assays of biomedically interesting compounds. Epinephrine and norfloxacin were taken as the model analytes. Epinephrine inhibited light emission from the AuNP-catalyzed CL while norfloxacin enhanced it. The CE-CL assays had detection limits of 6.9x10(-9) M for epinephrine and 7.3x10(-9) M for norfloxacin. It was noted that in the absence of AuNPs no CE-CL analytical signal was produced by epinephrine at 4.0x10(-5) M or norfloxacin at 1.5x10(-3) M under similar experimental conditions. Fluorescence spectroscopic measurements showed that although the fluorescence excitation/emission maxima remained the same, the fluorescence lifetime of luminol increased significantly in the presence of AuNPs (tau(2) increased from 8.49+/-0.12 to 9.18+/-0.047 ns in a two-exponential fit), indicating that the excited states of luminol molecules were stabilized through the interaction between luminol molecules and AuNPs. Finally, quantitation of epinephrine and norfloxacin in biological samples such as human urine by using the present AuNP-enhanced CE-CL method was demonstrated.

D-Amino acids in rat brain measured by liquid chromatography/tandem mass spectrometry.

Previous work has established that D-amino acids including D-serine (D-Ser) and D-aspartic acid (D-Asp) fulfill specific biological functions in the brain. In this work, the levels and anatomical distribution of d-amino acids in rat brain were determined by using an advantageous liquid chromatography/tandem mass spectrometric analytical method. The study was focused on D-Ser, D-Asp, and D-glutamic acid (D-Glu) because of the significance of L-Asp, L-Glu, and D-Ser in the nervous system. Prenatal, postnatal pups, and 90-day old rats were studied. Results indicated that D-Asp and D-Ser occurred in rat brain at the microg/g tissue level. However, D-Glu was not detected (< 110 ng/g tissue). Throughout the developmental stages d-Asp content in rat brain decreased rapidly from 9.42% of total Asp in 5-day prenatal rats to an undetectable level (< 150 ng/g tissue) in 90-day old rats. In contrast, D-Ser level increased gradually throughout the developmental stages. D-Ser percentage (D-Ser/(D-Ser + L-Ser)) changed from 4.94% in 5-day prenatal rats to 13.7% in 90-day old rats. Regional levels of D-Ser were found to be significantly higher in cortex, striatum, and hippocampus than in thalamus. D-Ser was not detected in cerebellum (< 172ng/g tissue).

Quantitation of cardioexcitatory Asn-D-Trp-Phe-NH2 diastereomers in Aplysia's central nervous system by nanoscale liquid chromatography-tandem mass spectrometry.

A tripeptide, Asn-D-Trp-Phe-NH(2) (NdWFa) that contains a D-amino acid residue (i.e. D-tryptophan) was previously identified in Aplysia's central nervous system (CNS) and found to be cardioexcitatory. However, the occurrence of its diastereomers including NWFa, theoretically the precursor of NdWFa, remains largely unknown. In this work, a nanoscale liquid chromatographic/tandem mass spectrometric (nano-LC-MS/MS) method was developed for a sensitive determination of the diastereomers of NWFa. Resolution of the diastereomers including NWFa, NdWFa, NWdFa, and dNWFa was achieved on capillary columns packed with C(18) silica particles with an MS detection-friendly mobile phase consisting of water, acetonitrile, and formic acid. Columns of different internal diameters (IDs) ranging from 75 to 250 microm were evaluated to achieve the best sensitivity. With the use of a 75 microm ID column integrated with a nanoelectrospray emitter, the method had limits of detection (LOD) of 0.21 nM (or 0.49 pg on column, 5 microl injected) NdWFa in tissue homogenate (S/N=3). The five major ganglia in Aplysia californica's CNS (i.e. buccal, cerebral, abdominal, plural, and pedal) were analyzed. NdWFa was detected only in abdominal ganglion at the ng/g tissue level. Further, its diastereomer, NWFa, was also detected for the first time and also only in abdominal ganglion at a significantly lower level. The levels of both NWFa and NdWFa varied from animal to animal in the range from 0 to 81 ng/g tissue.

A nanoparticle-based solid-phase extraction method for liquid chromatography-electrospray ionization-tandem mass spectrometric analysis.

A solid-phase extraction (SPE) procedure with the use of superparamagnetic Fe(3)O(4) nanoparticles as extracting agent was developed for HPLC-ESI-MS/MS analysis. Four most heavily used triazine pesticides (herbicides) were taken as the test compounds. The NPs showed an excellent capability to retain the compounds tested, and a quantitative extraction was achieved within 10min under the testing conditions, i.e. 100 microL NP solution was added to 400 mL sample in a beaker with stirring. After extraction, the superparamagnetic NPs were easily collected by using an external magnet. Very importantly, analytes retained on the Fe(3)O(4) NPs could be quantitatively recovered by dissolving the NPs with an HCl solution, allowing subsequent HPLC-ESI-MS/MS quantification. A capillary HPLC-ESI-MS/MS method with the present NP-based SPE procedure was developed for the determination of triazines including atrazine, prometryn, terbutryn, and propazine. Atrazine-d(5) was used as internal standard. The method had an LOD of 10 pg/mL atrazine, and a linear calibration curve over a range from 30 pg to 50.0 ng/mL. Simultaneous determination of the four triazine pesticides in water samples taken from local lakes was demonstrated.

Quantification of D-amino acids in the central nervous system of Aplysia californica by liquid chromatography/tandem mass spectrometry.

A sensitive, specific and reliable liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been developed for simultaneous determination of D-amino acids in the central nervous system (CNS) of Aplysia californica. In order to correct for any potential matrix effects on measured signals, deuterium-labeled L-Asp-d3 was used as an internal standard. Pre-column derivatization of the sample with 7-fluoro-4-nitrobenzoxadiazole (NBD-F) allowed both effective in-line pre-concentration and sensitive MS/MS detection of the analytes. An extraction column (50x0.25 mm, 5 microm C18 silica particles) was used to pre-concentrate/stack samples. Enantiomeric separation of amino acid enantiomers was achieved on a chiral column packed with teicoplanin aglycone bonded silica particles (170x0.25 mm, 5 microm) with an MS-friendly mobile phase. The characteristic precursor to product ion transitions, m/z 297-->279 (for NBD-Asp), m/z 269-->223 (For NBD-Ser), m/z 311-->293 (for NBD-Glu) and m/z 300-->282 (for NBD-L-Asp-d3) were monitored for the quantification. Samples from the CNS of A. californica and heart tissues were analyzed. D-Asp was detected at high levels in all the ganglia and nerve tissues, but not in the heart tissue. Further, neither D-Ser nor D-Glu was detected in Aplysia, a widely used neuronal model.

Assay of trace D-amino acids in neural tissue samples by capillary liquid chromatography/tandem mass spectrometry.

A sensitive chiral capillary HPLC-MS/MS method well suited for the determination of amino acid enantiomers in biological samples was developed. The method involved precolumn derivatization of the sample with 7-fluoro-4-nitrobenzoxadiazole (NBD-F). After derivatization, NBD-amino acids were stacked on a C18 reversed-phase extraction microcolumn, thus enriching and cleaning up the analytes. Various chiral stationary phases (CSPs) including cyclodextrin-bonded silica, Pirkle-type, vancomycin, and teicoplanin-bonded silica particles were evaluated for resolving NBD-F tagged amino acid enantiomers with mobile phases compatible with MS detection. It was found that only teicoplanin aglycon CSP provided sufficient resolution of NBD-Asp and NBD-Ser enantiomers to quantify trace levels of D-Asp and D-Ser in tissue samples. MS/MS detection of NBD-amino acid derivatives was very sensitive and selective. The high selectivity allowed the use of a stable isotope-labeled analyte analogue (i.e., L-aspartic acid-2,3,3-d3) as internal standard for the quantitation to improve assay reproducibility and reliability. Neural tissue samples dissected from rat brain and the central nervous system (CNS) of Aplysia californica, a widely used neuronal model, were analyzed to determine the chirality of glutamic acid (Glu), aspartic acid (Asp), and serine (Ser). The former two are major excitatory amino acids in the brain, and the last one has been recently identified as a neuromodulator. Both D-Ser and D-Asp were detected in rat brain. While the D-Asp level decreased rapidly through the developmental stages of the rat, the D-Ser level increased steadily from 82.3 microg/g of wet tissue in 3-day prenatal rats to 241.3 microg/g of wet tissue in 90-day-old rats. Interestingly, no D-Ser was detected in the CNS of Aplysia, a "primitive" invertebrate. However, the D-Asp level in this animal was found to be high. In a particular connective nerve sample, D-Asp was at 323.2 microg/g of wet tissue and constituted 60.2% of total Asp. D-Glu was not detected either in rat brain or in Aplysia's CNS.

Capillary liquid chromatography-tandem mass spectrometry of tetrahydroisoquinoline derived neurotoxins: a study on the blood-brain barrier of rat brain.

Certain tetrahydroisoquinoline derivatives such as 1-benzyl-1,2,3,4-tetrahydroisoquinoline (1-BnTIQ) and N-methylsalsolinol are parkinsonian neurotoxins. This paper describes a sensitive and reliable analytical method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the determination of tetrahydroisoquinoline derivatives (TIQs) in brain dialysate. Samples (20 microL injected) were effectively stacked and cleaned up in-line on a capillary column (5 cm x 0.25 mm I.D.) packed with 5 microm phenyl reversed-phase silica particles. Under the optimized conditions, electrospray ionisation-MS/MS detection of TIQs was highly sensitive. The capillary LC-MS/MS method had a detection limit of 2 ng/ml for TIQ. The method was used in combination with in vivo microdialysis to study the blood-brain barrier (BBB) for TIQs. The microdialysis probe was implanted in the frontal cortex of rat brain. Test compounds were administered intraperitoneally (i.p.). Four TIQs including 1,2,3,4-tetrahydroisoquinoline (TIQ), 5,6,7,8-tetrahydroisoquinoline (5-TIQ), 1-BnTIQ, and salsolinol (SAL) were studied. A concentration maximum was detected in brain dialysate for TIQ, 5-TIQ, and 1-BnTIQ about 40 min after drug administration. However, SAL, the precursor of N-methylsalsolinol was found unable to cross the BBB of rat brain.