Diamond surface functionalization via visible light-driven C-H activation for nanoscale quantum sensing

Nitrogen-vacancy (NV) centers in diamond are a promising platform for nanoscale NMR sensing. Despite significant progress toward using NV centers to detect and localize nuclear spins down to the single spin level, NV-based spectroscopy of individual, intact, arbitrary target molecules remains elusive. Such sensing requires that target molecules are immobilized within nanometers of NV centers with long spin coherence. The inert nature of diamond typically requires harsh functionalization techniques such as thermal annealing or plasma processing, limiting the scope of functional groups that can be attached to the surface. Solution-phase chemical methods can be readily generalized to install diverse functional groups, but they have not been widely explored for single-crystal diamond surfaces. Moreover, realizing shallow NV centers with long spin coherence times requires highly ordered single-crystal surfaces, and solution-phase functionalization has not yet been shown with such demanding conditions. In this work, we report a versatile strategy to directly functionalize C-H bonds on single-crystal diamond surfaces under ambient conditions using visible light, forming C-F, C-Cl, C-S, and C-N bonds at the surface. This method is compatible with NV centers within 10 nm of the surface with spin coherence times comparable to the state of the art. As a proof-of-principle demonstration, we use shallow ensembles of NV centers to detect nuclear spins from surface-bound functional groups. Our approach to surface functionalization opens the door to deploying NV centers as a tool for chemical sensing and single-molecule spectroscopy.

Halogen Bonding Interactions for Aromatic and Nonaromatic Explosive Detection

Improved sensing strategies are needed for facile, accurate, and rapid detection of aromatic and nonaromatic explosives. Density functional theory was used to evaluate the relative binding interaction energies between halogen-containing sensor model molecules and nitro-containing explosives. Interaction energies ranged from -18 to -14 kJ/mol and highly directional halogen bonding interactions were observed with bond distances ranging between 3.0 and 3.4 Å. In all geometry optimized structures, the sigma-hole of electropositive potential on the halogen aligned with a lone pair of electrons on the nitro-moiety of the explosive. The computational results predict that the strongest interactions will occur with iodine-based sensors as, of all the halogens studied, iodine is the largest, most polarizable halogen with the smallest electronegativity. Based on these promising proof-of-concept results, synthetically accessible sensors were designed using 1,4-dihalobenzene (X = Cl, Br, and I) with and without tetra-fluoro electron withdrawing groups attached to the benzene ring. These sensing molecules were embedded onto single walled carbon nanotubes that were mechanically abraded onto interdigitated array electrodes, and these were used to measure the responses to explosive model compounds cyclohexanone and dimethyl-dinitro-benzene in nitrogen gas. Amperometric current-time curves for selectors and control molecules, including concentration correlated signal enhancement, as well as response and recovery times, indicate selector responsiveness to these model compounds, with the largest response observed for iodo-substituted sensors.

The role of genetic variants in CRP in radiographic severity in African Americans with early and established rheumatoid arthritis

This study investigates the association of CRP (C-reactive protein) single-nucleotide polymorphisms (SNPs) with plasma CRP levels and radiographic severity in African Americans with early and established rheumatoid arthritis (RA). Using a cross-sectional case-only design, CRP SNPs were genotyped in two independent sets of African Americans with RA: Consortium for the Longitudinal Evaluation of African Americans with RA (CLEAR 1) and CLEAR 2. Radiographic data and CRP measurements were available for 294 individuals from CLEAR 1 (median (interquartile range (IQR) 25-75) disease duration of 1 (0.6-1.6) year) and in 407 persons from CLEAR 2 (median (IQR 25-75) disease duration of 8.9 (3.5-17.7) years). In CLEAR 1, in adjusted models, the minor allele of rs2808630 was associated with total radiographic score (incident rate ratio 0.37 (95% confidence interval (CI) 0.19-0.74), P-value=0.0051). In CLEAR 2, the minor allele of rs3093062 was associated with increased plasma CRP levels (P-value=0.002). For each rs3093062 minor allele, the plasma CRP increased by 1.51 (95% CI 1.15-1.95) mg dl(-1) when all the other covariates remained constant. These findings have important implications for assessment of the risk of joint damage in African Americans with RA.

Cigarette smoking, disease severity and autoantibody expression in African Americans with recent-onset rheumatoid arthritis

OBJECTIVE

To examine the association of smoking with clinical and serological features in African Americans with recent-onset rheumatoid arthritis (RA) and to explore whether this association is dependent on the presence of the HLA-DRB1 shared epitope (SE).

METHODS

In African Americans with recent-onset RA (n = 300), we examined the association of cigarette smoking (current versus past versus never and pack-years of exposure) with anti-cyclic citrullinated peptide antibody, rheumatoid factor (RF) (IgM and IgA), rheumatoid nodules and baseline radiographic erosions using logistic and cumulative logistic regression (adjusting for SE status). We also examined for evidence of interaction between smoking status and SE for all outcomes.

RESULTS

Although there was no association with RF-IgA seropositivity, current smokers were approximately twice as likely as never smokers to have higher IgA-RF concentrations (based on tertiles; OR = 1.74; 95% CI 1.05 to 2.88) and nodules (OR = 2.43; 95% CI 1.13 to 5.22). These associations were most pronounced in those with more than 20 pack-years of exposure. There was no association of smoking status or cumulative tobacco exposure with anti-cyclic citrullinated peptide antibody, IgM-RF or radiographic erosions. There was also no evidence of a biological or statistical SE-smoking interaction for any of the outcomes examined.

CONCLUSIONS

This is the first study to systematically examine the association of cigarette smoking with RA-related features in African Americans. Cigarette smoking is associated with both subcutaneous nodules and higher serum concentrations of IgA-RF in African Americans with RA, associations that may have important implications for long-term outcomes in this population.

Racial or ethnic differences in allele frequencies of single-nucleotide polymorphisms in the methylenetetrahydrofolate reductase gene and their influence on response to methotrexate in rheumatoid arthritis

BACKGROUND

The anti-folate drug methotrexate (MTX) is commonly used to treat rheumatoid arthritis.

OBJECTIVE

To determine the allele frequencies of five common coding single-nucleotide polymorphisms (SNPs) in the methylenetetrahydrofolate reductase (MTHFR) gene in African-Americans and Caucasians with rheumatoid arthritis and controls to assess whether there are differences in allele frequencies among these ethnic or racial groups and whether these SNPs differentially affect the efficacy or toxicity of MTX.

METHODS

Allele frequencies in the 677, 1298 and 3 additional SNPs in the MTHFR coding region in 223 (193 Caucasians and 30 African-Americans) patients with rheumatoid arthritis who previously participated in one of two prospective clinical trials were characterised, and genotypes were correlated with the efficacy and toxicity of MTX. Another 308 subjects with rheumatoid arthritis who participated in observational studies, one group predominantly Caucasian and the other African-American, as well as 103 normal controls (53 African-Americans and 50 Caucasians) were used to characterise allele frequencies of these SNPs and their associated haplotypes.

RESULTS

Significantly different allele frequencies were seen in three of the five SNPs and haplotype frequencies between Caucasians and African-Americans. Allele frequencies were similar between patients with rheumatoid arthritis and controls of the same racial or ethnic group. Frequencies of the rs4846051C, 677T and 1298C alleles were 0.33, 0.11 and 0.13, respectively, among African-Americans with rheumatoid arthritis. Among Caucasians with rheumatoid arthritis, these allele frequencies were 0.08 (p<0.001 compared with African-Americans with rheumatoid arthritis), 0.30 (p = 0.002) and 0.34 (p<0.001), respectively. There was no association between SNP alleles or haplotypes and response to MTX as measured by the mean change in the 28-joint Disease Activity Score from baseline values. In Caucasians, the 1298 A (major) allele was associated with a significant increase in MTX-related adverse events characteristic of a recessive genetic effect (odds ratio 15.86, 95% confidence interval 1.51 to 167.01; p = 0.021), confirming previous reports. There was an association between scores of MTX toxicity and the rs4846051 C allele, and haplotypes containing this allele, in African-Americans, but not in Caucasians.

CONCLUSIONS

: These results, although preliminary, highlight racial or ethnic differences in frequencies of common MTHFR SNPs. The MTHFR 1298 A and the rs4846051 C alleles were associated with MTX-related adverse events in Caucasians and African-Americans, respectively, but these findings should be replicated in larger studies. The rs4846051 SNP, which is far more common in African-Americans than in Caucasians, can also be proved to be a useful ancestry informative marker in future studies on genetic admixture.

Genetic risk factors for infection in patients with early rheumatoid arthritis

We analyzed clinical and genetic factors contributing to infections in 457 subjects with early rheumatoid arthritis (RA) enrolled in a prospective, 1-year clinical trial of methotrexate and the TNF inhibitor etanercept. Subjects were genotyped for the following single nucleotide polymorphisms (SNPs): (TNF -308, -238, and + 488); lymphotoxin-alpha (LTA) (LTA + 249, + 365, and + 720); and Fc gamma receptors FCGR2A 131 H/R; FCGR3A 176 F/V; and FCGR3B NA 1/2 and genotypes were correlated with infections. At least one URI was noted in 52% of subjects (99/191) with the NA2/NA2 genotype of the neutrophil-specific FCGR3B gene, compared to 42% (77/181) of those with the NA1/NA2 genotype and 39% (23/59) of those with the NA1/NA1 genotype (P = 0.038). Urinary tract infection (UTI) was associated with the TNF -238 A (odds ratio(OR) 2.56, 95% confidence interval (CI) 1.05-6.25) and LTA +365 C (OR 1.73, 95% CI 1.07-2.79) alleles, and marginally with the FCGR3A F allele (OR 1.72, 95% CI 0.99-3.00). There was a striking linear correlation between UTI and the number of risk alleles defined by these three SNPs (P < 0.001), suggesting an additive effect on susceptibility. These findings have important implications for the role of genetics in susceptibility to bacterial and viral infections.

Early rheumatoid arthritis in African-Americans: the CLEAR Registry

African-Americans have been under-represented in genetic studies of rheumatoid arthritis (RA) susceptibility and severity. Genetic and non-genetic factors influencing the radiographic severity of RA and its response to treatment are poorly understood, particularly in African-Americans. The Consortium for the Longitudinal Evaluation of African-Americans with early RA (CLEAR) Registry, a collaborative effort among four institutions in the southeast USA, will hopefully provide a useful resource to study these issues.

New therapeutic approaches to the management of rheumatoid arthritis

Rheumatoid arthritis (RA) is a common disease that affects up to 1% of the population, and causes significant morbidity and early mortality. The aetiology of RA is unknown; however, in the last 10 to 15 years significant advances in molecular technology have provided a greater understanding of the pathogenesis of the disease. This has led to the development of new approaches to the treatment of RA. The disease modifying antirheumatic oral agent leflunomide inhibits the proliferation of activated T cells that are important in the inflammation and degradation of synovial tissues. The 2 biological agents approved for the treatment of RA, infliximab and etanercept, are inhibitors of the pro-inflammatory cytokine, tumour necrosis factor-alpha (TNFalpha). Infliximab is a chimeric human/mouse monoclonal antibody which is administered by intravenous infusion and binds with high affinity to TNFalpha, thereby neutralising its effects. Etanercept is a recombinant, soluble TNF receptor molecule which is administered subcutaneously and binds to TNFalpha in the serum rendering it biologically inactive. The protein A immunoadsorption column is a medical device that in conjunction with plasmapheresis can be used in patients with refractory RA. These agents have provided new and effective therapies for the treatment of patients with RA.

Oligomeric structure of hepatic lipase: evidence from a novel epitope tag technique

The subunit structure of purified rHL (rHL) was determined by gel filtration chromatography, density gradient ultracentrifugation studies and a novel approach using epitope-tagged rHL. By gel filtration studies, native rHL had an apparent molecular weight of 179 kDa whereas enzyme treated with 6 M guanidine hydrochloride (GuHCl) for 22 h at room temperature gave a protein peak at 76 kDa. Using milder conditions for denaturation of rHL, such as 1 M GuHCl for 2 h, rHL eluted in two distinct peaks, one at 179 kDa and the other at 76 kDa. In addition, both protein peaks produced under mild denaturing conditions possessed detectable catalytic activity. Consistent with studies on lipoprotein lipase, the denatured rHL eluted from heparin-Sepharose at a lower salt concentration of 0.42 M NaCl than the native rHL which eluted at 0.72 M NaCl. By density gradient ultracentrifugation studies, the estimated molecular weight of native rHL was determined to be 113 kDa. Together, the data suggest that native rHL exists as a dimer that can be denatured into monomers by GuHCl and that a fraction of the denatured enzyme has detectable enzyme activity. To confirm these results, we designed two different rHL constructs that were epitope-tagged with either the myc or flag epitope and transfected them into 293 cells. The addition of the tag was shown not to alter enzyme secretion rate or specific activity of the lipase. Partially purified lipase from media of cotransfected cells was used to establish a dimer assay which employed a sandwich ELISA. This assay firmly established the presence of a rHL species which contained both the myc and flag tags, supporting an oligomeric subunit structure for rHL. Furthermore, the data using the epitope-tagged enzyme shows that this method could be a useful tool not only in identifying the region of the lipase responsible for dimer formation but also to study other protein-protein interactions.

Lack of secretion of retinyl ester by livers of normal and cholesterol-fed rabbits

The use of retinyl ester as a tracer for chylomicrons and chylomicron remnants depends on the observation that newly absorbed dietary retinol is transported as retinyl ester in plasma chylomicrons or chylomicron remnants and also on the assumption that organs other than intestine do not contribute retinyl ester to plasma. To measure the secretion of retinyl ester by rabbit liver, the liver was labeled by injecting labeled retinol intravenously 1) as a colloidal dose, 2) incorporated into liposomes or 3) dispersed in a solution of Tween 20. Depending on the dose, between 63 and 80% of the labeled retinol in the liver was esterified and was found in both parenchymal and nonparenchymal cells. For all types of doses in both normal and cholesterol-fed rabbits, less than 1% of the injected dose was present in the plasma as retinyl ester during the 24-hour time period after injection. The secretion of retinyl ester by liver in response to the uptake of retinyl ester-enriched chylomicrons was also measured. This was done by feeding a diet enriched in retinol followed by a retinol-free diet. Only an insignificant quantity of retinyl ester accumulated in plasma during a 24-hour period after blocking the removal of triglyceride-rich lipoproteins with Triton WR 1339. Apparently, there is little, if any, secretion of retinyl ester by the liver of normal or cholesterol-fed rabbits.

Exchange of retinyl and cholesteryl esters between lipoproteins of rabbit plasma

Normal or hypercholesterolemic rabbit plasma stimulates the transfer of retinyl ester as well as cholesteryl ester from rabbit lymph chylomicrons, chylomicron remnants or from cholesteryl ester-rich plasma VLDL to the d greater than 1.019 lipoprotein fractions. The presence of p-chloromercuriphenylsulfonate does not inhibit the transfer of these esters. Partially purified lipid transfer protein from rabbit or from human plasma also accelerates the transfer of the above esters. Whereas the rabbit plasma transfer protein preferentially accelerates the transfer of retinyl ester, the human plasma transfer protein appears to have a somewhat greater stimulating effect on the transfer of cholesteryl ester from low- to high-density lipoproteins.

Cholesteryl ester exchange protein in human plasma isolation and characterization

A protein catalyzing the exchange of cholesteryl esters among the lipoproteins was found in human plasma. A rapid method for assaying this activity was developed based on the transfer of radioactive cholesteryl esters from low density lipoprotein with MnCl2 in the presence of phosphate. Fractionation of plasma through a combination of ammonium sulfate precipitation, ultracentrifugation at p = 1.25, and chromatography on Phenyl-Sepharose, CM-cellulose, and concanavalin A-Sepharose, yielded a preparation purified 3500-fold compared to the starting plasma. The exchange protein was found to be a glycoprotein with an isoelectric point of 5 and apparent molecular weight of 80 000. On the basis of these properties and its immunological characteristics the exchange protein was judged to be distinct from any of the known apolipoproteins. This protein could also be separated from plasma phosphatidylcholine cholesterol acyl-transferase on DEAE-cellulose. The exchange protein did not appear to influence cholesterol esterification in lipoproteins by phosphatidylcholine cholesterol acyl-transferase, and the latter had no effect on the transfer of low density lipoprotein cholesteryl esters to high density lipoprotein. The exchange protein did not esterify cholesterol or hydrolyze cholesteryl esters in lipoproteins.

High plasma cholesterol in mink (Mustela vison) without atherosclerosis

Mink fed a commercial ration moderately high in cholesterol or fed a cholesterol-free semipurified diet have plasma cholesterol-free semipurified diet have plasma cholesterol concentrations similar to that found in human beings living in industrialized countries. In contrast with human beings, 80% of the plasma cholesterol in mink is carried in the high density lipoprotein fraction. Aortas and coronary arteries from animals up to 8 yr old were found to be free of fatty streaks and atherosclerotic plaques, both grossly and microscopically.

Stimulation of cholesterol ester exchange by lipoprotein-free rabbit plasma

A fraction in normal and hypercholesterolemic rabbit plasma of density greater than 1.25 stimulates the exchange of cholesterol esters between very low density and low density lipoproteins from hypercholesterolemic rabbit plasma. The exchange does not result from lecithin:cholesterol acyltransferase activity. The active factor appears to be a high molecular weight globulin with an isolelectric point of 5.2.

Validation of a dual-isotope plasma ratio method for measurement of cholesterol absorption in rats

Several methods for measuring cholesterol absorption in the rat have been compared. After administration of an oral dose of labeled cholesterol ((14)C or (3)H) and an intravenous dose of colloidal labeled cholesterol ((3)H or (14)C) the ratio of the two labels in plasma or whole blood 48 hr or more after dosing compared closely to the ratio of areas under the respective specific activity-time curves. The area ratio method is independent of a time lag between the appearance of oral and intravenous label in the bloodstream. Both measures of cholesterol absorption agree fairly well with a method based on measuring the unabsorbed dietary cholesterol in a pooled fecal sample. The plasma isotope ratio method gave more reproducible results than the fecal collection method when the measurement was repeated in the same animals 5 days after the first measurement. Cholesterol absorption was overestimated by the use of Tween 20-solubilized labeled cholesterol for the intravenous dose. The plasma disappearance curves of injected labeled colloidal cholesterol and cholesterol-labeled chylomicrons infused intravenously over a 3.5-hr period in the same animal coincided within experimental error from the first day until 75 days after injection. The plasma isotope ratio method for cholesterol absorption gave the same results in rats practicing coprophagy as in those in which this practice was prevented. The addition of sulfaguanidine to the diet lowered cholesterol absorption as measured by the plasma isotope ratio to the same degree as that measured by the fecal collection method.

Hypolipidemic effect of pregnancy in the rabbit

New Zealand white rabbits showed large decreases in plasma cholesterol and phospholipid concentrations during the second half of pregnancy. All lipoproteins (very low density, low density, and high density) participated in the decrease. Very large decreases in plasma cholesterol concentrations were observed even when the animals were maintained on high cholesterol diets. Increases in plasma cholesterol concentrations, after the intravenous administration of Triton WR 1339, were at least as great in pregnant as in nonpregnant animals. It is concluded that the decrease in plasma cholesterol concentrations is not the result of impaired plasma lipoprotein production.