The atomic metal core structures of the subnanometer clusters Au13PPh34S(CH2)11CH32Cl2 (1) and Au13PPh34S(CH2)11CH34 (2) were characterized using advanced methods of electron microscopy and X-ray ...absorption spectroscopy. The number of gold atoms in the cores of these two clusters was determined quantitatively using high-angle annular dark field scanning transmission electron microscopy. Multiple-scattering-path analyses of extended X-ray absorption fine structure (EXAFS) spectra suggest that the Au metal cores of each of these complexes adopt an icosahedral structure with a relaxation of the icosahedral strain. Data from microscopy and spectroscopy studies extended to larger thiolate-protected gold clusters showing a broader distribution in nanoparticle core sizes (183 ± 116 Au atoms) reveal a bulklike fcc structure. These results further support a model for the monolayer-protected clusters (MPCs) in which the thiolate ligands bond preferentially at 3-fold atomic sites on the nanoparticle surface, establishing an average composition for the MPC of Au180S(CH2)11CH340. Results from EXAFS measurements of a gold(I) dodecanethiolate polymer are presented that offer an alternative explanation for observations in previous reports that were interpreted as indicating Au MPC structures consisting of a Au core, Au2S shell, and thiolate monolayer.
Two syntheses of gold nanoparticles with fluorinated alkyl and aryl thiolate ligands are reported. The fluorous Au nanoparticles are smaller than previous gold fluor-capped examples, and are in the ...44−75 Au atom size range. Fluoroalkyl thiolate-protected (1H,1H,2H,2H-perfluorodecanethiolate) nanoparticles synthesized by a Brust reaction are a mixture of (mainly) ∼8.5 kDa (ca. 44 core atoms) and ∼14 kDa (ca. 75 core atoms) species, by MALDI-mass spectrometry. This composition is consistent with thermogravimetric analysis (TGA) results of the ligand shell composition. 19F NMR spectra display a progressive line broadening of resonances for fluorine sites closer to the Au core. A second synthetic route used a (ligand replacement) reaction of pentafluorobenzenethiol with Au55(PPh3)12Cl6. The exchange is (as previously observed for nonfluorinated thiols) accompanied by nanoparticle core size changes to produce a polydisperse mixture within which a Au75 core species could be electrochemically discerned by its characteristic 0.74 V electrochemical energy gap. Further characterization of the polydisperse nanoparticle product was done by HPLC, TEM, TGA, optical spectroscopy, and NMR data. Both varieties of fluorous nanoparticles exhibit solubilities typical of perfluorinated materials, as opposed to proteo versions.
We demonstrate the efficacy of ion-pair chromatography for separations of samples of charged, polydisperse, water-soluble gold nanoparticles protected by monolayers of N-acetyl-l-cysteine and of ...tiopronin ligands. These nanoparticle mixtures have 1−2-nm-diameter Au core sizes as estimated from UV−visible spectra of the separated components. This size range encompasses the transition from bulk metal to molecular properties. The nanoparticle mixtures were resolved, the smallest nanoparticles eluting first, on an octadecylsilyl (C18) column using isocratic elution with a methanol/water mobile phase containing tetrabutylammonium fluoride (Bu4N+F-) and phosphate buffer. The column retention increases with Bu4N+F- concentration, lowered pH, and decreasing methanol volume fraction. The retention mechanism is dominated by ion-pairing in either the mobile phase or at the stationary/mobile-phase interface. Size exclusion effects, used in many previous nanoparticle separations, are insignificant.
The synthesis and characterization of the clusters Au13PPh34S(CH2)11CH32Cl2 (1) and Au13PPh34S(CH2)11CH34 (2) are described. These mixed-ligand, sub-nanometer clusters, prepared via exchange of ...dodecanethiol onto phosphine-halide gold clusters, show enhanced stability relative to the parent. The characterization of these clusters features the precise determination of the number of gold atoms in the cluster cores using high-angle annular dark-field scanning transmission electron microscopy, allowing the assignment of 13 gold atoms (±3 atoms) to the composition of both cluster molecules. Electrochemical and optical measurements reveal discrete molecular orbital levels and apparent energy gaps of 1.6−1.7 eV for the two cluster molecules. The electrochemical measurements further indicate that the Au13PPh34S(CH2)11CH32Cl2 cluster undergoes an overall two-electron reduction. The electrochemical and spectroscopic properties of the two Au13 cluster molecules are compared with those of a secondary synthetic product, which proved to be larger Au thiolate-derivatized monolayer-protected clusters with an average core of Au180. The latter shows behavior fully consistent with the adoption of metallic-like properties.
This paper describes a new, organic-soluble 4-tert-butylbenzyl mercaptan (BBT) monolayer-protected silver cluster (AgBBT MPC) as the first example of a dissolved silver nanoparticle that exhibits ...quantized one-electron double layer charging (QDL) voltammetry. Polydisperse AgBBT MPCs made by two different synthetic protocols, but with similar average core diameters (2.1 nm), exhibit sharply differing electrochemistry and optical absorbance spectra. A two-phase procedure (organic/aqueous, termed Prep A-AgBBT) produced MPCs exhibiting a 475 nm surface plasmon absorbance and QDL voltammetry. Neither property was seen for MPCs made by a single-phase procedure, termed Prep B-AgBBT. The difference is thought to reflect poor passivation to oxide formation in the latter Prep B procedure, which is supported by X-ray photoelectron spectroscopy results. Thermogravimetry, mass spectra, and electrochemistry results suggest an average stoichiometric formula of Ag140BBT53, but transmission electron microscopy shows that the products are also polydisperse and include polycrystalline aggregates. Dry, cast films of both Ag MPC preparations on interdigitated array electrodes exhibit low electron hopping conductivity, compared to Au MPCs.
In February 2006, a diagnosis of sylvatic epidemic typhus in a counselor at a wilderness camp in Pennsylvania prompted a retrospective investigation. From January 2004 through January 2006, 3 more ...cases were identified. All had been counselors at the camp and had experienced febrile illness with myalgia, chills, and sweats; 2 had been hospitalized. All patients had slept in the same cabin and reported having seen and heard flying squirrels inside the wall adjacent to their bed. Serum from each patient had evidence of infection with Rickettsia prowazekii. Analysis of blood and tissue from 14 southern flying squirrels trapped in the woodlands around the cabin indicated that 71% were infected with R. prowazekii. Education and control measures to exclude flying squirrels from housing are essential to reduce the likelihood of sylvatic epidemic typhus.
Objective-To evaluate immunity induced by a multivalent vaccine containing a US Leptospira borgpetersenii serovar Hardjo type hardjo bovis (LHB) isolate in heifers challenged 12 months after ...vaccination. Design-Prospective vaccine challenge study. Animals-36 one-month old Holstein heifers. Procedures-18 heifers were vaccinated at 4 and 8 weeks of age with an inactivated vaccine containing Leptospira fractions. Additionally, 18 heifers were vaccinated at the same age with the same vaccine without any Leptospira fractions. All heifers were challenged with a US-origin LHB 12 months following booster vaccination. Urine samples were collected weekly for 8 weeks after challenge, and serum was collected at -1, 28, and 56 days after challenge for serologic testing. At 8 weeks after challenge, all heifers were necropsied, and kidney and reproductive system samples were collected for bacteriologic culture. Results-4 of 18 vaccinates had positive results of bacteriologic culture of urine samples, but only at 1 time point. All control heifers had positive results of bacteriologic culture of urine samples for at least 5 time points. Vaccinates had negative results of bacteriologic culture of kidney and reproductive system samples following necropsy, whereas all control heifers had positive results of bacteriologic culture of kidney samples and 5 of 18 had positive results of bacteriologic culture of reproductive system samples. Conclusions and Clinical Relevance-The vaccine administered to calves at 1 month of age prevented leptospire colonization of kidney and reproductive system tissue and significantly reduced urine shedding following challenge 12 months after vaccination. This vaccine provides an opportunity to protect calves at an early age from becoming infected and ultimately from becoming an LHB reservoir.
In 2017, there were almost 2.5 million high school students who experienced a concussion while playing a sport, raising concern for the neurologic problems that they could face. Some of these ...athletes may seek to gain a competitive advantage in their sport by utilizing substances like steroids. However, steroid use can cause increased aggression and body mass index (BMI), which might lead to heightened risk for concussions. Despite extensive research, we found no previous evidence linking these two factors.
This analysis aims to investigate steroid use trends in high school athletes and to determine whether there is an association between steroid use and concussions in these athletes.
We conducted a cross-sectional analysis of the cumulative Youth Risk Behavior Surveillance System (YRBSS). Respondents were added if they participated in sports and answered the steroid and concussion prompts. Demographic variables were assessed including age, grade, BMI, gender, and race/ethnicity.
We found that 3.7 % (n=2991) of high school athletes reported previous steroid use and that 20.7 % (n=2273) reported having sustained a concussion. There was a statistically significant difference in steroid use by race/ethnicity (p<0.001), with the highest rate of use (7.2 %) among American Indian/Alaska Natives (AI/AN). A significantly higher prevalence of steroid use occurred in athletes who were males (4.7 %) than females (2.5 %) and in athletes with a BMI>95 % (5.2 %) compared with those with a BMI between 85 and 95 % (3.9 %) and <85 % (3.5 %) (χ
=135.1, p<0.001 and χ
=16.3, p<0.001, respectively). Further, our results showed that the prevalence of steroid use among high school athletes decreased from 3.4 % in 1999 to 1.9 % in 2019, with the most drastic drop occurring between 2015 and 2019-declining 1.9 %. Whereas 19.6 % of athletes reported a concussion without steroid use, 54.6 % of steroid-utilizing athletes reported having experienced a concussion-a statistically significant finding (adjusted odds ratio AOR=4.3; 95 % CI: 3.2-5.9). Finally, compared with White athletes, we found that AI/AN athletes were significantly more likely to have sustained a concussion (AOR=2.3; 95 % CI=1.2-4.3).
Although our study found decreasing rates of steroid use among high school athletes from 1999 through 2019, our results also show that steroid use is significantly associated with sustaining a concussion. Additionally, the data from YRBSS also demonstrates that AI/AN high school athletes are more likely to utilize steroids and sustain a concussion. Given the long-term consequences of traumatic brain injuries, we recommend that coaches should be aware of potential steroid use among players, and that coaches, athletic trainers, and physicians should all be aware of concussion protocols and remove players from games for evaluation when a concussion is suspected.
We report reactivity of the gold nanoparticle TOA+ Au25(SC2Ph)181− (TOA+ = tetraoctylammonium; SC2Ph = phenylethanethiolate = L; Au25(SC2Ph)181− = Au25L18 1−) with Ag+, Cu2+, and Pb2+ ions. Titration ...of solutions of Au25L18 1− in CH2Cl2 with one and two equivalents of Ag+ produces changes in absorbance spectra with isosbestic points, and a titration curve break at 1:1 mol ratio, indicating a stoichiometric interaction. Similar effects are seen with Cu2+ and Pb2+ additions, but the break occurs at 0.5:1 mol ratio metal/nanoparticle. Changes in Au25L18 1− absorbance and fluorescence spectra are qualitatively similar to those accompanying oxidation of the Au25L18 1− nanoparticle anion, but the spectra of the stoichiometric products differ slightly according to the metal ion. Addition of higher excess of Ag+ or Cu2+ causes loss of characteristic Au25(SC2Ph)181− UV−vis spectral fine structure and apparent irreversible refining into larger nanoparticles. Voltammetric currents for nanoparticle 0/-1 and +1/0 redox waves are depressed by Ag+ addition. Electrospray ionization mass spectra of products of addition of up to two equivalents Ag+ show prominent peaks for Au25(SC2Ph)181− but also peaks corresponding to bimetal nanoparticles Au24Ag(SC2Ph)182+, Au23Ag2(SC2Ph)182+, and Au22Ag3(SC2Ph)182+. We propose a redox model of reaction of the Au25L18 1− nanoparticle with metal ions, in which the Au25L18 1− nanoparticle acts as a reductant toward the metal ion, forming Au25M(SC2Ph)18 adducts that become oxidatively dissociated in the mass spectral cationization environment to yield the bimetals observed.
An autosomal-dominant form of hyper-IgE syndrome caused by mutations in signal transducer and activator of transcription 3 is characterized by elevated IgE, eosinophilia, eczema, recurrent skin and ...pulmonary infections, and skeletal abnormalities.1 Recently, an autosomal recessive form of hyper-IgE syndrome caused by mutations in the dedicator of cytokinesis 8 (DOCK8) gene has been identified and is characterized by elevated IgE levels, eosinophilia, atopic dermatitis, asthma, food allergies, recurrent upper and lower respiratory tract infections, and unusual susceptibility to infections with herpesvirus family members (herpes simplex virus, human papilloma virus) and molluscum contagiosum.2,3 Cutaneous infections with human papilloma virus have progressed to squamous cell carcinomas in some cases. Furthermore, early diagnosis of this newly discovered immune deficiency before repeated infectious injury will likely optimize clinical outcomes after HCT. Because DOCK8 is expressed in both hematopoietic and nonhematopoietic tissues, further experience and long-term follow-up will be needed to determine whether correction of the hematopoietic compartment is sufficient to protect DOCK8-deficient patients from infection and cancer.
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