Multifaceted role of SARS-CoV-2 structural proteins in lung injury.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the third human coronavirus to cause acute respiratory distress syndrome (ARDS) and contains four structural proteins: spike, envelope, membrane, and nucleocapsid. An increasing number of studies have demonstrated that all four structural proteins of SARS-CoV-2 are capable of causing lung injury, even without the presence of intact virus. Therefore, the topic of SARS-CoV-2 structural protein-evoked lung injury warrants more attention. In the current article, we first synopsize the structural features of SARS-CoV-2 structural proteins. Second, we discuss the mechanisms for structural protein-induced inflammatory responses in vitro. Finally, we list the findings that indicate structural proteins themselves are toxic and sufficient to induce lung injury in vivo. Recognizing mechanisms of lung injury triggered by SARS-CoV-2 structural proteins may facilitate the development of targeted modalities in treating COVID-19.

Prognostic significance of serum globulin in patients with acute ischemic stroke.

BACKGROUND AND PURPOSE: We investigated the association between serum globulin levels upon hospital admission and in-hospital short-term outcomes in acute ischemic stroke (AIS) patients. METHODS: A total of 3,127 AIS patients enrolled from December 2013 to May 2014 across 22 hospitals in Suzhou city were included in the present study. We divided patients into 4 groups according to their level of admission serum globulin: Q1 (<23.5 g/L), Q2 (23.5-26.4 g/L), Q3 (26.4-29.9 g/L), and Q4 (≥29.9 g/L). Logistic regression models were used to estimate the effect of serum globulin on the short-term outcomes, including all cause in-hospital mortality, poor outcome upon discharge (modified Rankin Scale score ≥3) and in-hospital pneumonia in AIS patients. RESULTS: The median National Institutes of Health Stroke Scale (NIHSS) score was 4.0 (IQR, 2.0-7.0). The risk of in-hospital mortality was significantly higher in patients with highest serum globulin level (Q4) compared to those with lowest (Q1) (adjusted odds ratio [OR] 2.30; 95% confidence interval [CI], 1.12-4.70; P-trend =0.026). The highest serum globulin level (Q4) was associated with a 1.32-fold and 1.62-fold increase in the risk of poor outcome upon discharge (adjusted OR 1.32; 95% CI, 1.00-1.75; P-trend = 0.070) and in-hospital pneumonia (adjusted OR 1.62; 95% CI, 1.18-2.23; P-trend = 0.001) in comparison to Q1 after adjustment for potential covariates. CONCLUSIONS: A high level of serum globulin upon hospital admission was independently associated with all cause in-hospital mortality, poor outcome upon discharge and in-hospital pneumonia in relative mild AIS patients.

Effects of single atom doping on the ultrafast electron dynamics of M1Au24(SR)18 (M = Pd, Pt) nanoclusters.

Atomically precise, doped metal clusters are receiving wide research interest due to their synergistic properties dependent on the metal composition. To understand the electronic properties of doped clusters, it is highly desirable to probe the excited state behavior. Here, we report the ultrafast relaxation dynamics of doped M1@Au24(SR)18 (M = Pd, Pt; R = CH2CH2Ph) clusters using femtosecond visible and near infrared transient absorption spectroscopy. Three relaxation components are identified for both mono-doped clusters: (1) sub-picosecond relaxation within the M1Au12 core states; (2) core to shell relaxation in a few picoseconds; and (3) relaxation back to the ground state in more than one nanosecond. Despite similar relaxation pathways for the two doped nanoclusters, the coupling between the metal core and surface ligands is accelerated by over 30% in the case of the Pt dopant compared with the Pd dopant. Compared to Pd doping, the case of Pt doping leads to much more drastic changes in the steady state and transient absorption of the clusters, which indicates that the 5d orbitals of the Pt atom are more strongly mixed with Au 5d and 6s orbitals than the 4d orbitals of the Pd dopant. These results demonstrate that a single foreign atom can lead to entirely different excited state spectral features of the whole cluster compared to the parent Au25(SR)18 cluster. The detailed excited state dynamics of atomically precise Pd/Pt doped gold clusters help further understand their properties and benefit the development of energy-related applications.

Two distinctive energy migration pathways of monolayer molecules on metal nanoparticle surfaces.

Energy migrations at metal nanomaterial surfaces are fundamentally important to heterogeneous reactions. Here we report two distinctive energy migration pathways of monolayer adsorbate molecules on differently sized metal nanoparticle surfaces investigated with ultrafast vibrational spectroscopy. On a 5 nm platinum particle, within a few picoseconds the vibrational energy of a carbon monoxide adsorbate rapidly dissipates into the particle through electron/hole pair excitations, generating heat that quickly migrates on surface. In contrast, the lack of vibration-electron coupling on approximately 1 nm particles results in vibrational energy migration among adsorbates that occurs on a twenty times slower timescale. Further investigations reveal that the rapid carbon monoxide energy relaxation is also affected by the adsorption sites and the nature of the metal but to a lesser extent. These findings reflect the dependence of electron/vibration coupling on the metallic nature, size and surface site of nanoparticles and its significance in mediating energy relaxations and migrations on nanoparticle surfaces.

Chiral 38-gold-atom nanoclusters: synthesis and chiroptical properties.

Enantioselective synthesis of chiral Au38 nanoclusters is achieved with chiral 2-phenylpropane-1-thiol (abbreviated as R/S-PET, organic soluble), captopril and glutathione (water soluble) as the respective ligand. The circular dichroism (CD) spectra of Au38 (R-PET)24 and Au38 (S-PET)24 show multiple bands which are precisely mirror-imaged, while their normal optical absorption spectra are identical with each other and also superimposable with that of the racemic Au38 (SCH2 CH2 Ph)24 nanoclusters. The observed CD signals are not from the chiral ligands themselves (which only give rise to CD signals in the UV (<250 nm), rather than in the visible wavelength region). Chiral Au38 nanoclusters with different types of ligands are further compared. Although the Au38 core is intrinsically chiral, different chiral ligands are found to largely influence the chiroptical response of the overall nanocluster. Thus, the chiral response of ligand-protected nanoclusters has both contributions from the metal core and the ligand shell around it. These optically active nanoclusters hold promise in future applications such as chiral sensing and catalysis.

Supporting palladium metal on gold nanoparticles improves its catalysis for nitrite reduction.

Nitrate (NO3(-)) and nitrite (NO2(-)) anions are often found in groundwater and surface water as contaminants globally, especially in agricultural areas due to nitrate-rich fertilizer use. One popular approach to studying the removal of nitrite/nitrate from water has been their degradation to dinitrogen via Pd-based reduction catalysis. However, little progress has been made towards understanding how the catalyst structure can improve activity. Focusing on the catalytic reduction of nitrite in this study, we report that Au NPs supporting Pd metal ("Pd-on-Au NPs") show catalytic activity that varies with volcano-shape dependence on Pd surface coverage. At room temperature, in CO2-buffered water, and under H2 headspace, the NPs were maximally active at a Pd surface coverage of 80%, with a first-order rate constant (k(cat) = 576 L g(Pd)(-1) min(-1)) that was 15x and 7.5x higher than monometallic Pd NPs (~4 nm; 40 L g(Pd)(-1) min(-1)) and Pd/Al2O3 (1 wt% Pd; 76 L g(Pd)(-1) min(-1)), respectively. Accounting only for surface Pd atoms, these NPs (576 L g(surface-Pd)(-1) min(-1)) were 3.6x and 1.6x higher than monometallic Pd NPs (160 L g(surface-Pd)(-1) min(-1)) and Pd/Al2O3 (361 L g(surface-Pd)(-1) min(-1)). These NPs retained ~98% of catalytic activity at a chloride concentration of 1 mM, whereas Pd/Al2O3 lost ~50%. The Pd-on-Au nanostructure is a promising approach to improve the catalytic reduction process for nitrite and, with further development, also for nitrate anions.

CeO2-supported Au38(SR)24 nanocluster catalysts for CO oxidation: a comparison of ligand-on and -off catalysts.

The catalytic properties of atomically precise, thiolate-protected Au38(SR)24 (R = CH2CH2Ph) nanoclusters supported on CeO2 were investigated for CO oxidation in a fixed bed quartz reactor. Oxygen (O2) thermal pretreatment of Au38(SR)24/CeO2 at a temperature between 100 and 175 °C largely enhanced the catalytic activity, while pretreatment at higher temperatures (>200 °C) for removing thiolate instead gave rise to a somewhat lower activity than that for 175 °C pretreatment, and the ligand-off clusters were also found to be less stable. The CO conversion in the case of wet feed-gas (i.e. the presence of H2O vapor) was appreciably higher than the case of dry feed-gas when the reaction temperature was kept relatively low (between 60 and 80 °C), and interestingly the ligand-on and ligand-off catalysts exhibited opposite response to water vapor. Finally, we discussed some insights into the catalytic reaction involving the well-defined gold nanocluster catalyst.

Atomic-level alloying and de-alloying in doped gold nanoparticles.

Atomically precise alloying and de-alloying processes for the formation of Ag-Au and Cu-Au nanoparticles of 25-metal-atom composition (referred to as Ag(x)Au(25-x)(SR)18 and Cu(x)Au(25-x)(SR)18 , in which R = CH2CH2Ph) are reported. The identities of the particles were determined by matrix-assisted laser desorption ionization mass spectroscopy (MALDI-MS). Their structures were probed by fragmentation analysis in MALDI-MS and comparison with the icosahedral structure of the homogold Au25(SR)18 nanoparticles (an icosahedral Au13 core protected by a shell of Au12(SR)18). The Cu and Ag atoms were found to preferentially occupy the 13-atom icosahedral sites, instead of the exterior shell. The number of Ag atoms in Ag(x)Au(25-x)(SR)18 (x = 0-8) was dependent on the molar ratio of Ag(I)/Au(III) precursors in the synthesis, whereas the number of Cu atoms in Cu(x)Au(25-x)(SR)18 (x = 0-4) was independent of the molar ratio of Cu(II)/Au(III) precursors applied. Interestingly, the Cu(x)Au(25-x)(SR)18 nanoparticles show a spontaneous de-alloying process over time, and the initially formed Cu(x)Au(25-x)(SR)18 nanoparticles were converted to pure Au25(SR)18. This de-alloying process was not observed in the case of alloyed Ag(x)Au(25-x)(SR)18 nanoparticles. This contrast can be attributed to the stability difference between Cu(x)Au(25-x)(SR)18 and Ag(x)Au(25-x)(SR)18 nanoparticles. These alloyed nanoparticles are promising candidates for applications such as catalysis.

Total structure and electronic properties of the gold nanocrystal Au36(SR)24.

A golden opportunity: the total structure of a Au(36)(SR)(24) nanocluster reveals an unexpected face-centered-cubic tetrahedral Au(28) kernel (magenta). The protecting layer exhibits an intriguing combination of binding modes, consisting of four regular arch-like staples and the unprecedented appearance of twelve bridging thiolates (yellow). This unique protecting network and superatom electronic shell structure confer extreme stability and robustness.

Gold nanocluster-catalyzed selective oxidation of sulfide to sulfoxide.

Thiolate-protected gold nanoclusters are explored for catalytic application in the selective oxidation of sulfide to sulfoxide by PhIO. The TiO(2)-supported Au(25)(SR)(18) nanocluster catalysts give rise to high catalytic activity (e.g.∼97% conv. of Ph-S-CH(3) and ∼92% selectivity for Ph-S(=O)-CH(3) sulfoxide) and show excellent recyclability in the sulfoxidation process.

Monoplatinum doping of gold nanoclusters and catalytic application.

We report single-atom doping of gold nanoclusters (NCs), and its drastic effects on the optical, electronic, and catalytic properties, using the 25-atom system as a model. In our synthetic approach, a mixture of Pt(1)Au(24)(SC(2)H(4)Ph)(18) and Au(25)(SC(2)H(4)Ph)(18) was produced via a size-focusing process, and then Pt(1)Au(24)(SC(2)H(4)Ph)(18) NCs were obtained by selective decomposition of Au(25)(SC(2)H(4)Ph)(18) in the mixture with concentrated H(2)O(2) followed by purification via size-exclusion chromatography. Experimental and theoretical analyses confirmed that Pt(1)Au(24)(SC(2)H(4)Ph)(18) possesses a Pt-centered icosahedral core capped by six Au(2)(SC(2)H(4)Ph)(3) staples. The Pt(1)Au(24)(SC(2)H(4)Ph)(18) cluster exhibits greatly enhanced stability and catalytic activity relative to Au(25)(SC(2)H(4)Ph)(18) but a smaller energy gap (E(g) ≈ 0.8 eV vs 1.3 eV for the homogold cluster).

Evolution of nonlinear optical properties: from gold atomic clusters to plasmonic nanocrystals.

Atomic clusters of metals are an emerging class of extremely interesting materials occupying the intermediate size regime between atoms and nanoparticles. Here we report the nonlinear optical (NLO) characteristics of ultrasmall, atomically precise clusters of gold, which are smaller than the critical size for electronic energy quantization (∼2 nm). Our studies reveal remarkable features of the distinct evolution of the optical nonlinearity as the clusters progress in size from the nonplasmonic regime to the plasmonic regime. We ascertain that the smallest atomic clusters do not show saturable absorption at the surface plasmon wavelength of larger gold nanocrystals (>2 nm). Consequently, the third-order optical nonlinearity in these ultrasmall gold clusters exhibits a significantly lower threshold for optical power limiting. This limiting efficiency, which is superior to that of plasmonic nanocrystals, is highly beneficial for optical limiting applications.

CO oxidation catalyzed by oxide-supported Au25(SR)18 nanoclusters and identification of perimeter sites as active centers.

In this work, we explore the catalytic application of atomically monodisperse, thiolate-protected Au(25)(SR)(18) (where R = CH(2)CH(2)Ph) nanoclusters supported on oxides for CO oxidation. The solution phase nanoclusters were directly deposited onto various oxide supports (including TiO(2), CeO(2), and Fe(2)O(3)), and the as-prepared catalysts were evaluated for the CO oxidation reaction in a fixed bed reactor. The supports exhibited a strong effect, and the Au(25)(SR)(18)/CeO(2) catalyst was found to be much more active than the others. Interestingly, O(2) pretreatment of the catalyst at 150 °C for 1.5 h significantly enhanced the catalytic activity. Since this pretreatment temperature is well below the thiolate desorption temperature (~200 °C), the thiolate ligands should remain on the Au(25) cluster surface, indicating that the CO oxidation reaction is catalyzed by intact Au(25)(SR)(18)/CeO(2). We further found that increasing the O(2) pretreatment temperature to 250 °C (above the thiolate desorption temperature) did not lead to any further increase in activity at all reaction temperatures from room temperature to 100 °C. These results are in striking contrast with the common thought that surface thiolates must be removed-as is often done in the literature work-before the catalyst can exert high catalytic activity. The 150 °C O(2)-pretreated Au(25)(SR)(18)/CeO(2) catalyst offers ~94% CO conversion at 80 °C and ~100% conversion at 100 °C. The effect of water vapor on the catalytic performance is also investigated. Our results imply that the perimeter sites of the interface of Au(25)(SR)(18)/CeO(2) should be the active centers. The intact structure of the Au(25)(SR)(18) catalyst in the CO oxidation process allows one to gain mechanistic insight into the catalytic reaction.

Quantum sized gold nanoclusters with atomic precision.

Gold nanoparticles typically have a metallic core, and the electronic conduction band consists of quasicontinuous energy levels (i.e. spacing δ ≪ k(B)T, where k(B)T is the thermal energy at temperature T (typically room temperature) and k(B) is the Boltzmann constant). Electrons in the conduction band roam throughout the metal core, and light can collectively excite these electrons to give rise to plasmonic responses. This plasmon resonance accounts for the beautiful ruby-red color of colloidal gold first observed by Faraday back in 1857. On the other hand, when gold nanoparticles become extremely small (<2 nm in diameter), significant quantization occurs to the conduction band. These quantum-sized nanoparticles constitute a new class of nanomaterial and have received much attention in recent years. To differentiate quantum-sized nanoparticles from conventional plasmonic gold nanoparticles, researchers often refer to the ultrasmall nanoparticles as nanoclusters. In this Account, we chose several typical sizes of gold nanoclusters, including Au(25)(SR)(18), Au(38)(SR)(24), Au(102)(SR)(44), and Au(144)(SR)(60), to illustrate the novel properties of metal nanoclusters imparted by quantum size effects. In the nanocluster size regime, many of the physical and chemical properties of gold nanoparticles are fundamentally altered. Gold nanoclusters have discrete electronic energy levels as opposed to the continuous band in plasmonic nanoparticles. Quantum-sized nanoparticles also show multiple optical absorption peaks in the optical spectrum versus a single surface plasmon resonance (SPR) peak at 520 nm for spherical gold nanocrystals. Although larger nanocrystals show an fcc structure, nanoclusters often have non-fcc atomic packing structures. Nanoclusters also have unique fluorescent, chiral, and magnetic properties. Due to the strong quantum confinement effect, adding or removing one gold atom significantly changes the structure and the electronic and optical properties of the nanocluster. Therefore, precise atomic control of nanoclusters is critically important: the nanometer precision typical of conventional nanoparticles is not sufficient. Atomically precise nanoclusters are represented by molecular formulas (e.g. Au(n)(SR)(m) for thiolate-protected ones, where n and m denote the respective number of gold atoms and ligands). Recently, major advances in the synthesis and structural characterization of molecular purity gold nanoclusters have made in-depth investigations of the size evolution of metal nanoclusters possible. Metal nanoclusters lie in the intermediate regime between localized atomic states and delocalized band structure in terms of electronic properties. We anticipate that future research on quantum-sized nanoclusters will stimulate broad scientific and technological interests in this special type of metal nanomaterial.

Experimental and computational investigation of Au25 clusters and CO2: a unique interaction and enhanced electrocatalytic activity.

Atomically precise, inherently charged Au(25) clusters are an exciting prospect for promoting catalytically challenging reactions, and we have studied the interaction between CO(2) and Au(25). Experimental results indicate a reversible Au(25)-CO(2) interaction that produced spectroscopic and electrochemical changes similar to those seen with cluster oxidation. Density functional theory (DFT) modeling indicates these changes stem from a CO(2)-induced redistribution of charge within the cluster. Identification of this spontaneous coupling led to the application of Au(25) as a catalyst for the electrochemical reduction of CO(2) in aqueous media. Au(25) promoted the CO(2) → CO reaction within 90 mV of the formal potential (thermodynamic limit), representing an approximate 200-300 mV improvement over larger Au nanoparticles and bulk Au. Peak CO(2) conversion occurred at -1 V (vs RHE) with approximately 100% efficiency and a rate 7-700 times higher than that for larger Au catalysts and 10-100 times higher than those for current state-of-the-art processes.

Well-defined nanoclusters as fluorescent nanosensors: a case study on Au(25) (SG)(18).

The fluorescence of nanoparticles has attracted much attention in recent research, but in many cases the underlying mechanisms are difficult to evaluate due to the polydispersity of nanoparticles and their unknown structures, in particular the surface structures. Recent breakthroughs in the syntheses and structure determinations of well-defined gold nanoclusters provide opportunities to conduct in-depth investigations. Devising well-defined nanocluster sensors based on fluorescence change is of particular interest not only for scientific studies but also for practical applications. Herein, the potential of the glutathionate (SG)-capped Au(25) nanocluster as a silver ion sensor is evaluated. The Ag(+) detection limit of approximately 200 nM, based on the fluorescence enhancement and good linear fluorescence response in the silver ion concentration range from 20 nM to 11 µM, in combination with the good selectivity among 20 types of metal cations, makes Au(25) (SG)(18) a good candidate for fluorescent sensors for silver ions. Further experiments reveal three important factors responsible for the unique fluorescence enhancement caused by silver ions: 1) the oxidation state change of Au(25) (SG)(18) ; 2) the interaction of neutral silver species (Ag(0) , reduced by Au(25) (SG)(18) (-) ) with Au(25) (SG)(18) ; and 3) the interaction of Ag(+) with Au(25) (SG)(18.) Experiments demonstrate the very different chemistry of hydrophobic Au(25) (SC(2) H(4) Ph)(18) and hydrophilic Au(25) (SG)(18) in the reaction with silver ions. This work indicates another potential application of gold nanoclusters, offers new strategies for nanocluster-based chemical sensing, and reveals a new way to influence nanocluster chemistry for potential applications.

Atomically precise gold nanocrystal molecules with surface plasmon resonance.

Since Faraday's pioneering work on gold colloids, tremendous scientific research on plasmonic gold nanoparticles has been carried out, but no atomically precise Au nanocrystals have been achieved. This work reports the first example of gold nanocrystal molecules. Mass spectrometry analysis has determined its formula to be Au(333)(SR)(79) (R = CH(2)CH(2)Ph). This magic sized nanocrystal molecule exhibits fcc-crystallinity and surface plasmon resonance at approximately 520 nm, hence, a metallic nanomolecule. Simulations have revealed that atomic shell closing largely contributes to the particular robustness of Au(333)(SR)(79), albeit the number of free electrons (i.e., 333 - 79 = 254) is also consistent with electron shell closing based on calculations using a confined free electron model. Guided by the atomic shell closing growth mode, we have also found the next larger size of extraordinarily stability to be Au(~530)(SR)(~100) after a size-focusing selection--which selects the robust size available in the starting polydisperse nanoparticles. This work clearly demonstrates that atomically precise nanocrystal molecules are achievable and that the factor of atomic shell closing contributes to their extraordinary stability compared to other sizes. Overall, this work opens up new opportunities for investigating many fundamental issues of nanocrystals, such as the formation of metallic state, and will have potential impact on condensed matter physics, nanochemistry, and catalysis as well.

Chirality in gold nanoclusters probed by NMR spectroscopy.

We report the analysis of chirality in atomically precise gold nanoclusters by nuclear magnetic resonance (NMR) spectroscopic probing of the surface ligands. The Au(38)(SR)(24) and Au(25)(SR)(18) (where, R = CH(2)CH(2)Ph) are used as representative models for chiral and nonchiral nanoclusters, respectively. Interestingly, different (1)H signals for the two germinal protons in each CH(2) of the ligands on the chiral Au(38)(SR)(24) nanocluster were observed, so-called diastereotopicity. For α-CH(2) (closest to the chiral metal core), a chemical shift difference of up to ~0.8 ppm was observed. As for the nonchiral Au(25)(SCH(2)CH(2)Ph)(18)(-)TOA(+) nanocluster, no diastereotopicity was detected (i.e., no chemical shift difference for the two protons in the CH(2)), confirming the Au(25) core being nonchiral. These two typical examples demonstrate that NMR spectroscopy can be a useful tool for investigating chirality in Au nanoclusters. Since the diastereotopicity induced on the methylene protons by chiral nanoclusters is independent of the enantiomeric composition of the chiral particles, NMR can probe the chirality of the nanoclusters even in the case of a racemic mixture, while circular dichroism spectroscopy is not useful for racemic mixtures.

Crystal structures of Au2 complex and Au25 nanocluster and mechanistic insight into the conversion of polydisperse nanoparticles into monodisperse Au25 nanoclusters.

We previously reported a size-focusing conversion of polydisperse gold nanoparticles capped by phosphine into monodisperse [Au(25)(PPh(3))(10)(SC(2)H(4)Ph)(5)Cl(2)](2+) nanoclusters in the presence of phenylethylthiol. Herein, we have determined the crystal structure of [Au(25)(PPh(3))(10)(SC(2)H(4)Ph)(5)Cl(2)](2+) nanoclusters and also identified an important side-product-a Au(I) complex formed in the size focusing process. The [Au(25)(PPh(3))(10)(SC(2)H(4)Ph)(5)Cl(2)](2+) cluster features a vertex-sharing bi-icosahedral core, resembling a rod. The formula of the Au(I) complex is determined to be [Au(2)(PPh(3))(2)(SC(2)H(4)Ph)](+) by electrospray ionization (ESI) mass spectrometry, and its crystal structure (with SbF(6)(-) counterion) reveals Au-Au bridged by -SC(2)H(4)Ph and with terminal bonds to two PPh(3) ligands. Unlike previously reported [Au(2)(PR(3))(2)(SC(2)H(4)Ph)](+) complexes in the solid state, which exist as tetranuclear complexes (i.e., dimers of [Au(2)(PR(3))(2)(SC(2)H(4)Ph)](+) units) through a Au···Au aurophilic interaction, in our case we found that the [Au(2)(PPh(3))(2)(SC(2)H(4)Ph)](+) complex exists as a single entity, rather than being dimerized to form a tetranuclear complex. The observation of this Au(I) complex allows us to gain insight into the intriguing conversion process from polydisperse Au nanoparticles to monodisperse Au(25) nanoclusters.

Synthesis and electrospray mass spectrometry determination of thiolate-protected Au55(SR)31 nanoclusters.

Since the pioneering work of Schmid et al. on phosphine-capped Au(55) clusters, the search for thiolated Au(55) has long been of major interest. This work reports the synthesis and electrospray ionization mass spectrometry (ESI-MS) evidence of Au(55)(SCH(2)CH(2)Ph)(31) clusters.