Laser Desorption Postionization Mass Spectrometry Imaging of Folic Acid Molecules in Tumor Tissue

Mass spectrometry imaging (MSI) is an innovative and powerful tool in biomedical research. It is well-known that folic acid (FA) has a high affinity for folic acid receptor (FR), which is overexpressing in epithelial cancer. Herein, we propose a novel method to diagnose cancer through direct mapping of the label-free FA spatial distribution in tissue sections by state-of-the-art laser desorption postionization-mass spectrometry imaging (LDPI-MSI). Compared with other tumor imaging methods, such as fluorescence imaging, photoacoustic imaging (PAI), magnetic resonance imaging (MRI), and micro-SPECT/CT, complicated synthesis and labeling processes are not required. The LDPI-MSI was performed on 30 μm thick sections from a murine model of breast cancer (inoculation of 4T1 cells) that were predosed with 20 mg/kg of FA. The image obtained from the characteristic mass spectrometric signature of FA at <i>m</i>/<i>z</i> 265 illustrated that FA was concentrated primarily in tumor tissue and displayed somewhat lower retention in adjacent normal controls. The results suggest that the proposed method could be used potentially in cancer diagnosis

Size Growth of Au₄Cu₄: From Increased Nucleation to Surface Capping

The size conversion of atomically precise metal nanoclusters is fundamental for elucidating structure-property correlations. In this study, copper salt (CuCl)-induced size growth from [Au4Cu4(Dppm)2(SAdm)5]+ (abbreviated as [Au4Cu4S5]+) to [Au4Cu6(Dppm)2(SAdm)4Cl3]+ (abbreviated as [Au4Cu6S4Cl3]+) (SAdmH = 1-adamantane mercaptan, Dppm = bis-(diphenylphosphino)methane) was investigated via experiments and density functional theory calculations. The [Au4Cu4S5]+ adopts a defective pentagonal bipyramid core structure with surface cavities, which could be easily filled with the sterically less hindered CuCl and CuSCy (i.e., core growth) (HSCy = cyclohexanethiol) but not the bulky CuSAdm. As long as the Au4Cu5 framework is formed, ligand exchange or size growth occurs easily. However, owing to the compact pentagonal bipyramid core structure, the latter growth mode occurs only for the surface-capped [Au4Cu6(Dppm)2(SAdm)4Cl3]+ structure (i.e., surface-capped size growth). A preliminary mechanistic study with density functional theory (DFT) calculations indicated that the overall conversion occurred via CuCl addition, core tautomerization, Cl migration, the second [CuCl] addition, and [CuCl]-[CuSR] exchange steps. And the [Au4Cu6(Dppm)2(SAdm)4Cl3]+ alloy nanocluster exhibits aggregation-induced emission (AIE) with an absolute luminescence quantum yield of 18.01% in the solid state. This work sheds light on the structural transformation of Au–Cu alloy nanoclusters induced by Cu(I) and contributes to the knowledge base of metal-ion-induced size conversion of metal nanoclusters

How a Single Electron Affects the Properties of the “Non-Superatom” Au₂₅ Nanoclusters

In this study, we successfully synthesized the rod-like [Au₂₅(PPh₃)₁₀(SePh)₅Cl₂]^<i>q</i> (<i>q</i> = +1 or +2) nanoclusters through kinetic control. The single crystal X-ray crystallography determined their formulas to be [Au₂₅(PPh₃)₁₀(SePh)₅Cl₂]­(SbF₆) and [Au₂₅(PPh₃)₁₀(SePh)₅Cl₂]­(SbF₆)­(BPh₄), respectively. Compared to the previously reported Au₂₅ coprotected by phosphine and thiolate ligands (i.e., [Au₂₅(PPh₃)₁₀(SR)₅Cl₂]²⁺), the two new rod-like Au₂₅ nanoclusters show some interesting structural differences. Nonetheless, each of these three nanoclusters possesses two icosahedral Au₁₃ units (sharing a vertex gold atom) and the bridging “Au–Se­(S)–Au” motifs. The compositions of the two new nanoclusters were characterized with ESI-MS and TGA. The optical properties, electrochemistry, and magnetism were studied by EPR, NMR, and SQUID. All these results demonstrate that the valence character significantly affects the properties of the “non-superatom” Au₂₅ nanoclusters, and the changes are different from the previously reported “superatom” Au₂₅ nanoclusters. Theoretical calculations indicate that the extra electron results in the half occupation of the highest occupied molecular orbitals in the rod-like Au₂₅⁺ nanoclusters and, thus, significantly affects the electronic structure of the “non-superatom” Au₂₅ nanoclusters. This work offers new insights into the relationship between the properties and the valence of the “non-superatom” gold nanoclusters

How a Single Electron Affects the Properties of the “Non-Superatom” Au₂₅ Nanoclusters

In this study, we successfully synthesized the rod-like [Au₂₅(PPh₃)₁₀(SePh)₅Cl₂]^<i>q</i> (<i>q</i> = +1 or +2) nanoclusters through kinetic control. The single crystal X-ray crystallography determined their formulas to be [Au₂₅(PPh₃)₁₀(SePh)₅Cl₂]­(SbF₆) and [Au₂₅(PPh₃)₁₀(SePh)₅Cl₂]­(SbF₆)­(BPh₄), respectively. Compared to the previously reported Au₂₅ coprotected by phosphine and thiolate ligands (i.e., [Au₂₅(PPh₃)₁₀(SR)₅Cl₂]²⁺), the two new rod-like Au₂₅ nanoclusters show some interesting structural differences. Nonetheless, each of these three nanoclusters possesses two icosahedral Au₁₃ units (sharing a vertex gold atom) and the bridging “Au–Se­(S)–Au” motifs. The compositions of the two new nanoclusters were characterized with ESI-MS and TGA. The optical properties, electrochemistry, and magnetism were studied by EPR, NMR, and SQUID. All these results demonstrate that the valence character significantly affects the properties of the “non-superatom” Au₂₅ nanoclusters, and the changes are different from the previously reported “superatom” Au₂₅ nanoclusters. Theoretical calculations indicate that the extra electron results in the half occupation of the highest occupied molecular orbitals in the rod-like Au₂₅⁺ nanoclusters and, thus, significantly affects the electronic structure of the “non-superatom” Au₂₅ nanoclusters. This work offers new insights into the relationship between the properties and the valence of the “non-superatom” gold nanoclusters

Total Structure Determination of Au₂₁(S-Adm)₁₅ and Geometrical/Electronic Structure Evolution of Thiolated Gold Nanoclusters

The larger size gold nanoparticles typically adopt a face-centered cubic (fcc) atomic packing, while in the ultrasmall nanoclusters the packing styles of Au atoms are diverse, including fcc, hexagonal close packing (hcp), and body-centered cubic (bcc), depending on the ligand protection. The possible conversion between these packing structures is largely unknown. Herein, we report the growth of a new Au₂₁(S-Adm)₁₅ nanocluster (S-Adm = adamantanethiolate) from Au₁₈(SR)₁₄ (SR = cyclohexylthiol), with the total structure determined by X-ray crystallography. It is discovered that the hcp Au₉-core in Au₁₈(SR)₁₄ is transformed to a fcc Au₁₀-core in Au₂₁(S-Adm)₁₅. Combining with density functional theory (DFT) calculations, we provide critical information about the growth mechanism (geometrical and electronic structure) and the origin of fcc-structure formation for the thiolate-protected gold nanoclusters

Putative pathway of flower development in <i>S. sebiferum</i>.

<p>External (vernalization, photoperiod) and internal (autonomous, age, gibberellins) signals integrate into elaborate genetic network to regulate flowering. The genes components of the genetic network have been discussed in text.</p

Main orthologs involved in abotic stress response.

<p>Main orthologs involved in abotic stress response.</p

Flower development stages in <i>S. sebiferum</i>.

<p><i>S. sebiferum</i> flower development can be divided into six fine stages: a. inflorescence bud swelling; b. inflorescence emergence; c. inflorescence expansion; d. staminate flower partially open with pistillate flower buds emergence; e. staminate flower fully open with pistillate flower buds expansion; f. pistillate flower fully open. Scale bar = 1 cm. Red arrow represents pistillate flower bud and black arrow represents pistillate flowers.</p

Flower Bud Transcriptome Analysis of <i>Sapium sebiferum</i> (Linn.) Roxb. and Primary Investigation of Drought Induced Flowering: Pathway Construction and G-Quadruplex Prediction Based on Transcriptome

<div><p><i>Sapium sebiferum</i> (Linn.) Roxb. (Chinese Tallow Tree) is a perennial woody tree and its seeds are rich in oil which hold great potential for biodiesel production. Despite a traditional woody oil plant, our understanding on <i>S. sebiferum</i> genetics and molecular biology remains scant. In this study, the first comprehensive transcriptome of <i>S. sebiferum</i> flower has been generated by sequencing and <i>de novo</i> assembly. A total of 149,342 unigenes were generated from raw reads, of which 24,289 unigenes were successfully matched to public database. A total of 61 MADS box genes and putative pathways involved in <i>S. sebiferum</i> flower development have been identified. Abiotic stress response network was also constructed in this work, where 2,686 unigenes are involved in the pathway. As for lipid biosynthesis, 161 unigenes have been identified in fatty acid (FA) and triacylglycerol (TAG) biosynthesis. Besides, the G-Quadruplexes in RNA of <i>S. sebiferum</i> also have been predicted. An interesting finding is that the stress-induced flowering was observed in <i>S. sebiferum</i> for the first time. According to the results of semi-quantitative PCR, expression tendencies of flowering-related genes, <i>GA1</i>, <i>AP2</i> and <i>CRY2</i>, accorded with stress-related genes, such as <i>GRX50435</i> and <i>PRXⅡ39562</i>. This transcriptome provides functional genomic information for further research of <i>S. sebiferum</i>, especially for the genetic engineering to shorten the juvenile period and improve yield by regulating flower development. It also offers a useful database for the research of other <i>Euphorbiaceae</i> family plants.</p></div

Drought induced flowering (right) and analysis of the expression of related genes by semi-quantitative PCR (left).

<p>Under drought stress, one-year-old seedling (+ in right) began to bloom (red arrow indicating the staminate flowers of <i>S. sebiferum</i>) and normal control (CK at the left) performed no flower or flower bud on the shoot apex (white arrow). Besides the difference of flower, the precocious-flowering seedling had distinct phonotype of senescence, such as dark leaf color and withered leaf tips. The expression of genes related with flowering and drought stress has been analyzed by semi-quantity PCR, and detailed discussion has been shown in text. le, <u>le</u>aves tissue; flo, <u>flo</u>wer tissue.</p