Publications by authors named "Ruowei Jiang"

15 Publications

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Comparing the self-perceived effects of a facial anti-aging product to those automatically detected from selfie images of Chinese women of different ages and cities.

Skin Res Technol 2021 Apr 6. Epub 2021 Apr 6.

ModiFace, A L'Oréal Group Company, Toronto, ON, Canada.

Objective: To assess the agreement, after 1-month application of a popular and efficient anti-aging product, between self-perceived facial signs of aging and those detected and graded by an automatic A.I-based system, using smartphones' selfie images.

Material And Methods: Of 1065 Chinese women, aged 18-60 years, from eight different Chinese cities were recruited. They were asked to apply daily, for 1 month, a referential anti-aging product onto their whole face. Selfie images were taken by all subjects at D and D and sent to our facilities for being analyzed through 10 different facial signs. At D , all subjects were asked to fill a questionnaire on the status of their faces, through six general statements.

Results: A global agreement between both approaches is reached, particularly among women older than 40 years where the severity of facial signs is already more pronounced or among younger women who present at least facial signs scored above one grading units. This limit becomes, therefore, a prerequisite in the recruitment of Chinese subjects in the case of anti-aging applied studies and possible automatically based on automatic grading system. When respecting such conditions, the positive effects of the product on most facial signs can be demonstrated after 28 days of successive applications.

Conclusion: Such methodological approach paves the road in fulfilling the need of consumers of a better transparency in the claims of an anti-aging product.
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http://dx.doi.org/10.1111/srt.13037DOI Listing
April 2021

Japanese experiment of a complete and objective automatic grading system of facial signs from selfie pictures: Validation with dermatologists and characterization of changes due to age and sun exposures.

Skin Res Technol 2020 Dec 27. Epub 2020 Dec 27.

L'Oréal Research and Innovation, Clichy, France.

Objective: To evaluate the capacity of the automatic detection system to accurately grade, from smartphones' selfie pictures, the severity of ten facial signs in Japanese women and their changes due to age and sun exposures.

Methods: A three-step approach was conducted, based on self-taken selfie images. At first, to check on 310 Japanese women (18-69 years) enrolled in the northerner Hokkaido area (latitude 43.2°N), how, on ten facial signs, the A.I-based automatic grading system may correlate with dermatological assessments, taken as reference. Second, to assess and compare age changes in 310 Japanese and 112 Korean women. Third, as these Japanese panelists were recruited according to their usual behavior toward sun exposure, that is, non-sun-phobic (NSP, N = 114) and sun-phobic (SP, N = 196), and through their regular and early use of a photo-protective product, to characterize the facial photo-damages.

Results: (a) On the ten facial signs, detected automatically, nine were found significantly (P < .0001) highly correlated with the evaluations made by three Japanese dermatologists (Wrinkles: r = .75; Sagging: r = .80; Pigmentation: r = .75). (b) The automatic scores showed significant changes with age, by decade, of Wrinkles/Texture, Pigmentation, and Ptosis/Sagging (P < .05). (c) After 45 years, a significantly increased severity of Wrinkles/Texture and Pigmentation was observed in NSP vs. SP women (P < .05). A trend of an increased Ptosis/Sagging (P = .09) was observed.

Conclusion: This work illustrates, for the first time through investigations conducted at home, some impacts of aging and sun exposures on facial signs of Japanese women. Results significantly confirm the importance of sun avoidance coupled with photo-protective measures. In epidemiological studies, the AI-based system offers a fast, affordable, and confidential approach in detection and quantification of facial signs and their dependence with ages, environments and lifestyles.
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http://dx.doi.org/10.1111/srt.12982DOI Listing
December 2020

Monitoring of adsorption and transfer of organochlorines in soybean seeds and sprouts with mass spectrometric imaging.

Anal Chim Acta 2020 Sep 22;1130:10-19. Epub 2020 Jul 22.

Laboratory of Mass Spectrometry, College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, PR China; Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, PR China. Electronic address:

Development of analytical techniques that can monitor the adsorption, transfer and in-situ distribution of environmental pollutants in agricultural products is essential to ensure the implementation of stringent food safety standards for consumer protection. A mass spectrometric imaging approach is described herein to investigate the dynamic changes and spatial distributions of 4, 4'-DDT (dichlorodiphenyltrichloroethane) in soybean seeds and sprouts during the growth. Soy beans seeds incubated in DDT containing water were sliced in every 20 μm and directly blotted on the surface of a compressed thin film of (BiO)(CoO)(ZnO) nanoparticles. Endogenous molecules and exogenous DDT compounds in soy bean seeds were ionized and dissociated by photoelectrons that are generated on surfaces of semiconductor nanoparticles upon the irradiation of the 3rd harmonic (355 nm) of Nd:YAG laser. Structural identification is achieved by the interpretation of fragment ions resulting from electron-initiated specific bond cleavages or hole oxidization. Mass spectrometric images reveal increased quantities of DDT residues in soy bean seeds and sprouts during the growth. It provides an in situ way without extensive sample preparation to monitor the transfer and distribution of exogenous pollutants as well as the possible impacts on plant growth.
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http://dx.doi.org/10.1016/j.aca.2020.07.011DOI Listing
September 2020

The continuous development of a complete and objective automatic grading system of facial signs from selfie pictures: Asian validation study and application to women of three ethnic origins, differently aged.

Skin Res Technol 2021 Mar 20;27(2):183-190. Epub 2020 Jul 20.

ModiFace - A L'Oréal Group Company, Toronto, ON, Canada.

Objective: To evaluate the capacity of the automatic detection system to accurately grade, from smartphones' selfie pictures, the severity of seven new facial signs added to the nine previously integrated.

Methods: A two-step approach was conducted: first, to check on 112 Korean women, how the AI-based automatic grading system may correlate with dermatological assessments, taken as reference; second, to confirm on 1140 women of three ancestries (African, Asian, and Caucasian) the relevance of the newly input facial signs.

Results: The sixteen specific Asian facial signs, detected automatically, were found significantly (P < .0001) highly correlated with the clinical evaluations made by two Korean dermatologists (wrinkles: r = .90; sagging: r = .75-.95; vascular: r = .85; pores: r = .60; pigmentation: r = .50-.80). When applied at a larger scale on women of different ethnicities, new signs were found of good accuracy and reproducibility, albeit depending on ethnicity. Due to contrast with the innate skin complexion, the facial signs dealing with skin pigmentation were found of a much higher relevance among Asian women than African or Caucasian women. The automatic gradings were even found of a slightly higher accuracy than the clinical gradings.

Conclusion: The previously used automatic grading system is now completed by adding new facial signs apt at being detected. The continuous development is now integrating some limitations with regard to the constitutive skin complexion of the self-pictured subjects. Presenting reproducible assessments, highly correlated with medical grading, this system could change tremendously clinical researches, like in epidemiological studies, where it offers an easy, fast, affordable, and confidential approach in the objective quantification of facial signs.
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http://dx.doi.org/10.1111/srt.12922DOI Listing
March 2021

Real-time laser induced chemical derivatizations of peptide N-Terminus for in-situ mass spectrometric sequencing at sub-picomole and nanosecond scale.

Anal Chim Acta 2020 Mar 13;1100:1-11. Epub 2019 Dec 13.

Laboratory of Mass Spectrometry, College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, PR China; Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, PR China. Electronic address:

Distinguishing b- and y-ions is essential to compute amino acid sequences from either N- or C-terminus in mass spectrometry. We described herein a solvent free and real time on-plate derivatization approach that can tag N-terminus of peptides at microliter level with p-chlorobenzaldehyde or 2-hydroxy-5-methylisophthalaldehyde for matrix assisted laser desorption ionization mass spectrometry (MALDI MS). Less than 1 μL of sample solutions can be directly mixed with equal volumes of p-chlorobenzaldehyde or 2-hydroxy-5-methylisophthalaldehyde and α-cyano-4-hydroxycinnamic acid (CHCA), a matrix compound to co-crystalize with analytes for efficient absorption of laser energy and peptide ionization. When the mixture spotted on the sample plate is irradiated with the 3rd harmonic (355 nm) of Nd:YAG laser pulses (3 ns width), N-terminal amine groups of peptides instantly react with carbonyl groups of chlorobenzaldehyde or 2-hydroxy-5-methylisophthalaldehyde. Resultant peptides carrying with on-plate formed azomethine group (-CN-) are simultaneously protonated and isolated as precursor ions for subsequent collision-activated dissociation. The mass shift with unique Cl isotopic signature unambiguously distinguishes b ions from y ions and other ions. This method does not need extensive sample preparation and is useful for those samples with limited quantities down to sub-picomole level in sub-microliter volumes. The efficiency was demonstrated with synthetic peptides and tryptic peptides of model proteins. It was found that 2-hydroxy-5-methylisophthalaldehyde provides improved yield for peptides containing lysine residues. Unknown proteins of human saliva and bovine milk as well as phosphopeptides have been identified.
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http://dx.doi.org/10.1016/j.aca.2019.12.029DOI Listing
March 2020

Mass spectrometric imaging reveals photocatalytic degradation intermediates of aromatic organochlorines resulting from interfacial photoelectron transfer and hydroxyl radical abstraction on semiconductor nanoparticles.

Anal Chim Acta 2019 Apr 21;1054:104-113. Epub 2018 Dec 21.

Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, PR China. Electronic address:

Organochlorines are highly persistent and toxic contaminants that are widely distributed and accumulated in various aquatic or soil environments as well as food chains. Heterogeneous photocatalytic degradation of such pollutants by using semiconductor nanoparticles has been recognized as one of the effective purification ways. Understanding of degradation mechanisms and designing of highly efficient semiconductor nanoparticles require structural identification of various degradation intermediates that are difficult to achieve with current spectroscopic techniques. Herein a mass spectrometric approach was developed to tackle interfacial photoelectron transfer and hydroxyl radical abstraction on different semiconductor nanoparticles. Chlorobenzenes (including hexachlorobenzene and chlorothalonil) adsorbed on the surfaces of nanoparticles were found to instantly undergo dechlorination and ring dissociation through photoelectron capture dissociation and abstraction of a chlorine atom from aromatic C-Cl bond by hydroxyl radicals. Different intermediates have been unambiguously identified with experimental evidences provided by a Q-TOF mass spectrometer. It has been demonstrated that both electron density around atoms and steric effects of side chains contribute to the site selectivity for photoelectron capture and hydroxyl radical abstraction. But the energies needed for chemical bond cleavages and the stabilization of acquired charges play important roles in degradation efficiency. By using mass spectrometric imaging, photocatalytic differences of different semiconductor nanoparticles have been revealed.
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http://dx.doi.org/10.1016/j.aca.2018.12.032DOI Listing
April 2019

A new procedure, free from human assessment that automatically grades some facial skin structural signs. Comparison with assessments by experts, using referential atlases of skin ageing.

Int J Cosmet Sci 2019 Feb;41(1):67-78

ModiFace - A L'Oréal Group Company, Toronto, Canada.

Objective: To develop an automatic system that grades the severity of facial signs through 'selfies' pictures taken by women of different ages and ethnics.

Methods: 1140 women from three ethnics (African-American, Asian, Caucasian), of different ages (18-80 years old), took 'selfies' by high resolution smartphones cameras under different conditions of lighting or facial expressions. A dedicated software, was developed, based on a Convolutional Neural Network (CNN) that integrates training data from referential Skin Aging Atlases. The latter allows to an immediate quantification of the severity of nine facial signs according to the ethnicity declared by the subject. These automatic grading were confronted to those assessed by 12 trained experts and dermatologists either on 'selfies' pictures or in live conditions on a smaller cohort of women.

Results: The system appears weakly influenced by lighting conditions or facial expressions (coefficients of variations ranging 10-13% for most signs) and leads to global agreements with experts' assessments, even showing a better reproducibility on some facial signs.

Conclusion: This automatic scoring system, still in development, seems offering a new quantitative approach in the quantified description of facial signs, independent from human vision, in many applications, being individual, cosmetic oriented or dermatological with regard to the follow-up of medical anti-ageing corrective strategies.
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http://dx.doi.org/10.1111/ics.12512DOI Listing
February 2019

Electron Acceptive Mass Tag for Mass Spectrometric Imaging-Guided Synergistic Targeting to Mice Brain Glutamate Receptors.

ACS Chem Neurosci 2019 01 31;10(1):757-767. Epub 2018 Dec 31.

Mass Spectrometry Center for Structural Identification of Biological Molecules and Precision Medicine Institute of Public Health and Molecular Medicine Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, College of Chemistry , Central China Normal University , Wuhan , Hubei 430079 , P. R. China.

Dysfunctional glutamate receptors (GluRs) have been implicated in neurological disorders and injuries. Hetero-tetrameric assemblies of different GluR subunits or splicing variants have distinct spatiotemporal expression patterns and pharmacological properties. Mass spectrometric imaging of GluRs-targeted small molecules is important for determining the regional preferences of these compounds. We report herein the development of a mass tag covalently bonded with glutamate or N-methyl-d-aspartate that functions as both an electron acceptor to generate mass spectrometric signals on irradiated (BiO)(CoO)(ZnO) nanoparticles with the third harmonic (355 nm) of Nd:YAG laser and as the core component to target bilobed clamshell-like structures of GluRs. In this approach, different molecules produce the same tag ion. It provides a new avenue for quantitative assessment of spatial densities of different compounds, which cannot be achieved with well-established stable isotope labeling technique due to different ionization efficiency of different compounds. Various coexisting endogenous molecules are also simultaneously detected for investigation of overall physiological changes induced by these compounds. Because semiconductors do not generate background peaks, this method eliminates interferences from organic matrix materials that are used in regular MALDI (matrix assisted laser desorption ionization). The localized ionization provides high spatial resolution that can be down to sub-micrometers.
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http://dx.doi.org/10.1021/acschemneuro.8b00580DOI Listing
January 2019

Ion fragmentations via photoelectron activated radical relays and competed hole oxidization on semiconductor nanoparticles for mass spectrometry.

Anal Chim Acta 2018 Dec 13;1044:1-11. Epub 2018 Jun 13.

Mass Spectrometry Center for Structural Identification of Biological Molecules and Precision Medicine, Institute of Public Health and Molecular Medicine, Key Laboratory of Pesticides and Chemical Biology of Ministry of Education of China, College of Chemistry, Central China Normal University, 152 Luoyu Road, Wuhan, Hubei 430079, PR China. Electronic address:

Structural identification is challenging in mass spectrometric imaging because of inadequate sample quantities and limited sampling time in each pixel for tandem mass spectrometry (MS/MS) experiments, which are usually used for the generation of fragment ions. We report herein the observation of a cascade of highly specific chemical bond cleavages via a low-energy photoelectron activated radical relays and a competed hole oxidization on surfaces of (BiO)(CoO)(ZnO) semiconductor nanoparticles irradiated with the 3rd harmonic (355 nm) of the Nd: YAG laser. Distinguished from high energy electron impact (EI), this approach generates gaseous radical anions through the exothermic capture of low-energy tunneling electrons that are not able to cause extensive vibrational excitations. It was found not only original radical center but also secondary or even tertiary radical centers cause specific bond cleavages exclusively on α positions. The original radical center directly activates the cleavages of α-positioned chemical bonds that cause the formation of secondary radical centers. Ion fragmentations proceed along the newly formed radical centers that further activate the cleavages of their α-positioned chemical bonds. Using 8 compounds, we have demonstrated various radical reactions involved in desulfonation, cyclization, and ring contraction reactions as well as competed hole oxidization-generated hydroxyl radical substitution reactions. The interpretable fragment ions provide unambiguous experimental evidences for structural elucidation of drug residues and metabolites in mass spectrometric imaging of tissue slices without tandem mass spectrometry (MS/MS).
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http://dx.doi.org/10.1016/j.aca.2018.06.033DOI Listing
December 2018

Carbon emissions induced by land-use and land-cover change from 1970 to 2010 in Zhejiang, China.

Sci Total Environ 2019 Jan 23;646:930-939. Epub 2018 Jul 23.

College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, Zhejiang, China. Electronic address:

Land-use and land-cover change (LUCC) is a crucial factor affecting carbon emissions. Zhejiang Province has witnessed unprecedented LUCC concomitant with rapid urbanization from 1970 to 2010. In this study, remote sensing, geographic information system (GIS) and the Intergovernmental Panel on Climate Change (IPCC) method were combined to quantify changes in both vegetation carbon storage and soil organic carbon (SOC) storage resulting from LUCC during 1970-1990 and 1990-2010. For both 1970-1990 and 1990-2010, the results showed successive decrease in farmlands (2.8 × 10 ha or -9.15% and 5.9 × 10 ha or -20.49%, respectively) and grasslands (3.4 × 10 ha or -10.73% and 1.5 × 10 ha or -54.1%, respectively), and continuous increase in forests (2.0 × 10 ha or 0.33% and 1.7 × 10 ha or 2.81%, respectively) and built-up lands (2.07 × 10 ha or 78.41% and 6.49 × 10 ha or 137.8%, respectively). From 1970 to 1990, approximately 8.3 Tg of the total carbon sink declined, including a 0.4 Tg reduction in vegetation carbon and a 7.9 Tg reduction in SOC. While from 1990 to 2010, approximately 17.5 Tg of carbon storage declined, comprising a 2.8 Tg of carbon accumulated by vegetation, and a 20.3 Tg reduction in SOC. Overall, LUCC has resulted in huge amount of carbon emissions in Zhejiang from 1970 to 2010. Efficient planning for LUCC and gradual mitigation of carbon emissions are indispensable for future urban development in China under increasing pressure from global warming.
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http://dx.doi.org/10.1016/j.scitotenv.2018.07.317DOI Listing
January 2019

Mass spectrometric monitoring of interfacial photoelectron transfer and imaging of active crystalline facets of semiconductors.

Nat Commun 2017 02 22;8:14524. Epub 2017 Feb 22.

Mass Spectrometry Center for Structural Identification of Biological Molecules and Precision Medicine, Institute of Public Health and Molecular Medicine Analysis, Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, China.

Monitoring of interfacial electron transfer (ET) in situ is important to understand the ET mechanism and designing efficient photocatalysts. We describe herein a mass spectrometric approach to investigate the ultrafast transfer of photoelectrons that are generated by ultraviolet irradiation on surfaces of semiconductor nanoparticles or crystalline facets. The mass spectrometric approach can not only untargetedly detect various intermediates but also monitor their reactivity through associative or dissociative photoelectron capture dissociation, as well as electron detachment dissociation of adsorbed molecules. Proton-coupled electron transfer and proton-uncoupled electron transfer with radical initiated polymerization or hydroxyl radical abstraction have been unambiguously demonstrated with the mass spectrometric approach. Active crystalline facets of titanium dioxide for photocatalytic degradation of juglone and organochlorine dichlorodiphenyltrichloroethane are visualized with mass spectrometry imaging based on ion scanning and spectral reconstruction. This work provides a new technique for studying photo-electric properties of various materials.
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http://dx.doi.org/10.1038/ncomms14524DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5322523PMC
February 2017

Imaging of Endogenous Metabolites of Plant Leaves by Mass Spectrometry Based on Laser Activated Electron Tunneling.

Sci Rep 2016 Apr 7;6:24164. Epub 2016 Apr 7.

Mass Spectrometry Center for Structural Identification of Biological Molecules and Precision Medicine, Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, P. R. China.

A new mass spectrometric imaging approach based on laser activated electron tunneling (LAET) was described and applied to analysis of endogenous metabolites of plant leaves. LAET is an electron-directed soft ionization technique. Compressed thin films of semiconductor nanoparticles of bismuth cobalt zinc oxide were placed on the sample plate for proof-of-principle demonstration because they can not only absorb ultraviolet laser but also have high electron mobility. Upon laser irradiation, electrons are excited from valence bands to conduction bands. With appropriate kinetic energies, photoexcited electrons can tunnel away from the barrier and eventually be captured by charge deficient atoms present in neutral molecules. Resultant unpaired electron subsequently initiates specific chemical bond cleavage and generates ions that can be detected in negative ion mode of the mass spectrometer. LAET avoids the co-crystallization process of routinely used organic matrix materials with analyzes in MALDI (matrix assisted-laser desorption ionization) analysis. Thus uneven distribution of crystals with different sizes and shapes as well as background peaks in the low mass range resulting from matrix molecules is eliminated. Advantages of LAET imaging technique include not only improved spatial resolution but also photoelectron capture dissociation which produces predictable fragment ions.
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http://dx.doi.org/10.1038/srep24164DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4823709PMC
April 2016

Titanium Dioxide Photocatalytic Polymerization of Acrylamide for Gel Electrophoresis (TIPPAGE) of Proteins and Structural Identification by Mass Spectrometry.

Sci Rep 2016 Feb 11;6:20981. Epub 2016 Feb 11.

Mass Spectrometry Center for Structural Identification of Biological Molecules and Precision Medicine, Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, P. R. China.

Polyacrylamide gel electrophoresis (PAGE) coupled with mass spectrometry has been well established for separating, identifying and quantifying protein mixtures from cell lines, tissues or other biological samples. The copolymerization process of acrylamide and bis-acrylamide is the key to mastering this powerful technique. In general, this is a vinyl addition reaction initiated by free radical-generating reagents such as ammonium persulfate (APS) and tetramethylethylenediamine (TEMED) under basic pH and degassing experimental condition. We report herein a photocatalytic polymerization approach that is based on photo-generated hydroxyl radicals with nanoparticles of titanium dioxide. It was shown that the polymerization process is greatly accelerated in acidic condition when ultraviolet light shots on the gel solution containing TiO2 nanoparticles without degassing. This feature makes it very useful in preparing Triton X-100 acid urea (TAU) gel that has been developed for separating basic proteins such as histones and variants in acidic experimental condition. Additionally, the presence of titanium dioxide in the gel not only improves mechanistic property of gels but also changes the migration pattern of different proteins that have different affinities to titanium dioxide.
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http://dx.doi.org/10.1038/srep20981DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4750088PMC
February 2016

Laser Activated Electron Tunneling Based Mass Spectrometric Imaging of Molecular Architectures of Mouse Brain Revealing Regional Specific Lipids.

Anal Chem 2016 Jan 14;88(1):732-9. Epub 2015 Dec 14.

Mass Spectrometry Center for Structural Identification of Biological Molecules and Precision Medicine, Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University , Wuhan, Hubei 430079, People's Republic of China.

A comprehensive description of overall brain architecture at the molecular level is essential for understanding behavioral and cognitive processes in health and diseases. Although fluorescent labeling of target proteins has been successfully established to visualize a brain connectome, the molecular basis for diverse neurophysiological phenomena remains largely unknown. Here we report a brain-wide, molecular-level, and microscale imaging of endogenous metabolites, in particular, lipids of mouse brain by using laser activated electron tunneling (LAET) and mass spectrometry. In this approach, atomic electron emission along with finely tuned laser beam size provides high resolution that can be down to the sub-micrometer level to display spatial distribution of lipids in mouse brain slices. Electron-directed soft ionization has been achieved through exothermal capture of tunneling photoelectrons as well as unpaired electron-initiated chemical bond cleavages. Regionally specific lipids including saturated, mono-unsaturated, and poly-unsaturated fatty acids as well as other lipids, which may be implicated in neurological signaling pathways, have been discovered by using this laser activated electron tunneling based mass spectrometric imaging (LAET-MSI) technique.
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http://dx.doi.org/10.1021/acs.analchem.5b02871DOI Listing
January 2016

Photo-catalytic activities of plant hormones on semiconductor nanoparticles by laser-activated electron tunneling and emitting.

Sci Rep 2015 Mar 9;5:8893. Epub 2015 Mar 9.

Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, P. R. China.

Understanding of the dynamic process of laser-induced ultrafast electron tunneling is still very limited. It has been thought that the photo-catalytic reaction of adsorbents on the surface is either dependent on the number of resultant electron-hole pairs where excess energy is lost to the lattice through coupling with phonon modes, or dependent on irradiation photon wavelength. We used UV (355 nm) laser pulses to excite electrons from the valence band to the conduction band of titanium dioxide (TiO₂), zinc oxide (ZnO) and bismuth cobalt zinc oxide (Bi₂O₃)₀.₀₇(CoO)₀.₀₃(ZnO)₀.₉ semiconductor nanoparticles with different photo catalytic properties. Photoelectrons are extracted, accelerated in a static electric field and eventually captured by charge deficient atoms of adsorbed organic molecules. A time-of-flight mass spectrometer was used to detect negative molecules and fragment ions generated by un-paired electron directed bond cleavages. We show that the probability of electron tunneling is determined by the strength of the static electric field and intrinsic electron mobility of semiconductors. Photo-catalytic dissociation or polymerization reactions of adsorbents are highly dependent on the kinetic energy of tunneling electrons as well as the strength of laser influx. By using this approach, photo-activities of phytohormones have been investigated.
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http://dx.doi.org/10.1038/srep08893DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4352873PMC
March 2015