The Journal of Steroid Biochemistry and Molecular Biology, 2015
Steroid concentrations in stimulated follicular fluid (sFF) samples have been linked to the quali... more Steroid concentrations in stimulated follicular fluid (sFF) samples have been linked to the quality of oocytes used in IVF treatments. Most of the published studies focused on evaluating the association of the IVF outcomes with only a few of the steroids, measured by immunoassays (IA). We performed a treatment outcome, prospective cohort study using stimulated FF sampled from 14 infertile women undergoing IVF treatment; single oocyte was used per IVF cycle. Fourteen endogenous steroids were analyzed in 22 ovarian follicle aspirations, which corresponded to the embryos used in the IVF. Ten oocytes were associated with live birth (LB) and 12 with no pregnancy (NP). Steroids were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. Differences in distribution of concentrations in association with the pregnancy outcome (LB or NP), and receiver operating characteristic (ROC) curves analysis were performed for the entire cohort and for within-women data. The predominant androgen and estrogen in stimulated sFF were androstenedione (A4) and estradiol (E2), respectively. Lower concentrations of pregnenolone (Pr), lower ratios of A4/ dehydroepiandrosterone (DHEA), testosterone (Te)/DHEA, and greater ratios of E2/Te, and estrone/A4 were observed in sFF samples associated with LB. Among the oocytes associated with NP, in four out of 12 samples total concentration of androgens was above the distribution of the concentrations in the oocytes corresponding to the LB group. Observations of the study indicated increased consumption of precursors and increased biosynthesis of estrogens in the follicles associated with LB. Our data suggest that potentially steroid profiles in sFF obtained during oocyte retrieval may serve as biomarkers for selection of the best embryo to transfer after IVF.
ABSTRACT Mild (capillary) interface conditions which do not completely desolvate the ions of prot... more ABSTRACT Mild (capillary) interface conditions which do not completely desolvate the ions of proteins in electrospray ionization mass spectrometry (ESI-MS) may be required to probe the higher order structures and weak associations. For the small protein bovine ubiquitin, two ion distributions (unsolvated ions and unresolved solvated ions) were observed. The resolvable solvation for leucine-enkephalin with methanol and water shows that the use of countercurrent N{sub 2} flow at the capillary affects the solvation observed. 2 figs. (DLC)
To answer the questions: Are perinatal reproductive hormone profiles different in case of a twin ... more To answer the questions: Are perinatal reproductive hormone profiles different in case of a twin compared with a singleton pregnancy? Are reproductive endocrine profiles of twin girls influenced by their male co-twin and vice versa? Prospective cohort study from January 2004 to October 2009. Not applicable. A total of 204 mothers of twins and 248 singleton control subjects, aged >18 years, pregnant with a twin or singleton and no endocrine disease or malignancy. Blood samples were collected at mid-gestation from the mother and at delivery from the mothers and the umbilical cords. Estrogens, androgens, SHBG, progesterone, and gonadotropins were measured. Hormonal profiles were compared between singletons and twins, different types of twins, and opposite-sex and same-sex twins. Estrogen and progesterone concentrations were higher in mothers of twins compared with singletons, but twin babies had lower estrogen and progesterone concentrations at birth. Opposite-sex twin girls did not...
Mild (capillary) interface conditions which do not completely desolvate the ions of proteins in e... more Mild (capillary) interface conditions which do not completely desolvate the ions of proteins in electrospray ionization mass spectrometry (ESI-MS) may be required to probe the higher order structures and weak associations. For the small protein bovine ubiquitin, two ion distributions (unsolvated ions and unresolved solvated ions) were observed. The resolvable solvation for leucine-enkephalin with methanol and water shows that the use of countercurrent N{sub 2} flow at the capillary affects the solvation observed. 2 figs. (DLC)
Clinica chimica acta; international journal of clinical chemistry, Jan 2, 2015
Mass spectrometry coupled to liquid chromatography (LC-MS and LC-MS/MS) is an analytical techniqu... more Mass spectrometry coupled to liquid chromatography (LC-MS and LC-MS/MS) is an analytical technique that has rapidly grown in popularity in clinical practice. In contrast to traditional technology, mass spectrometry is superior in many respects including resolution, specificity, multiplex capability and has the ability to measure analytes in various matrices. Despite these advantages, LC-MS/MS remains high cost, labor intensive and has limited throughput. This specialized technology requires highly trained personnel and therefore has largely been limited to large institutions, academic organizations and reference laboratories. Advances in automation will be paramount to break through this bottleneck and increase its appeal for routine use. This article reviews these challenges, shares perspectives on essential features for LC-MS/MS total automation and proposes a step-wise and incremental approach to achieve total automation through reducing human intervention, increasing throughput ...
The technique of electrospray ionization (ESI) has significantly extended the ability to characte... more The technique of electrospray ionization (ESI) has significantly extended the ability to characterize large molecules by mass spectrometry. Proteins to at least 200,000 D can be transferred intact to the gas phase and molecular weights determined with precisions as high as 0.001% if individual charge states can be resolved. The ESI-MS can also serve as a near ideal interface and
Journal of The American Society for Mass Spectrometry, 2015
Mass spectrometry enables the study of increasingly larger biomolecules with increasingly higher ... more Mass spectrometry enables the study of increasingly larger biomolecules with increasingly higher resolution, which is able to distinguish between fine isotopic variants having the same additional nucleon count, but slightly different masses. Therefore, the analysis of the fine isotopic distribution becomes an interesting research topic with important practical applications. In this paper, we propose the comprehensive methodology for studying the basic characteristics of the fine isotopic distribution. Our approach uses a broad spectrum of methods ranging from generating functions-that allow us to estimate the variance and the information theory entropy of the distribution-to the theory of thermal energy fluctuations. Having characterized the variance, spread, shape, and size of the fine isotopic distribution, we are able to indicate limitations to high resolution mass spectrometry. Moreover, the analysis of "thermorelativistic" effects (i.e., mass uncertainty attributable to relativistic effects coupled with the statistical mechanical uncertainty of the energy of an isolated ion), in turn, gives us an estimate of impassable limits of isotopic resolution (understood as the ability to distinguish fine structure peaks), which can be moved further only by cooling the ions. The presented approach highlights the potential of theoretical analysis of the fine isotopic distribution, which allows modeling the data more accurately, aiming to support the successful experimental measurements. Graphical Abstract ᅟ.
Serum testosterone can be measured by LC-MS/MS and RIA. We investigated whether the testosterone-... more Serum testosterone can be measured by LC-MS/MS and RIA. We investigated whether the testosterone-fracture relationship was affected by the method of measurement. We measured total testosterone (TT) by LC-MS/MS (TTLC-MS/MS) and RIA (TTRIA) in serum samples collected from 602 men whose incident fractures had been continuously ascertained by x-ray reports from 1989 to 2010. We measured bone mineral density (BMD) by dual-energy x-ray absorptiometry. The association between TT and fracture risk was assessed by the Cox proportional hazards model, taking into account the effect of age and BMD. Mean TTLC-MS/MS was higher than TTRIA by 27 ng/dL (95% CI 13-41). The concordance correlation coefficient between TTLC-MS/MS and TTRIA was 0.72 (95% CI 0.68-0.76). The Deming regression equation linking the 2 measurements was ln(TTLC-MS/MS + 10) = 0.87 + 0.87 × ln(TTRIA + 10). The hazard ratio of fracture per SD decrease in TT was 1.32 (95% CI 1.12-1.54) for TTLC-MS/MS and 1.23 (1.06-1.43) for TTRIA....
Methods in molecular biology (Clifton, N.J.), 2013
Isotopic information determined by mass spectrometry can be used in a wide variety of application... more Isotopic information determined by mass spectrometry can be used in a wide variety of applications. Broadly speaking these could be classified as "passive" applications, meaning that they use naturally occurring isotopic information, and "active" applications, meaning that the isotopic distributions are manipulated in some way. The classic passive application is the determination of chemical composition by comparing observed isotopic patterns of molecules to theoretically calculated isotopic patterns. Active applications include isotope exchange experiments of a variety of types, as well as isotope labeling in tracing studies and to provide references for quantitation. Regardless of the type of application considered, the problem of theoretical calculation of isotopic patterns almost invariably arises. This paper reviews a number of application examples and computational approaches for isotopic studies in mass spectrometry.
The Journal of Steroid Biochemistry and Molecular Biology, 2015
Steroid concentrations in stimulated follicular fluid (sFF) samples have been linked to the quali... more Steroid concentrations in stimulated follicular fluid (sFF) samples have been linked to the quality of oocytes used in IVF treatments. Most of the published studies focused on evaluating the association of the IVF outcomes with only a few of the steroids, measured by immunoassays (IA). We performed a treatment outcome, prospective cohort study using stimulated FF sampled from 14 infertile women undergoing IVF treatment; single oocyte was used per IVF cycle. Fourteen endogenous steroids were analyzed in 22 ovarian follicle aspirations, which corresponded to the embryos used in the IVF. Ten oocytes were associated with live birth (LB) and 12 with no pregnancy (NP). Steroids were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. Differences in distribution of concentrations in association with the pregnancy outcome (LB or NP), and receiver operating characteristic (ROC) curves analysis were performed for the entire cohort and for within-women data. The predominant androgen and estrogen in stimulated sFF were androstenedione (A4) and estradiol (E2), respectively. Lower concentrations of pregnenolone (Pr), lower ratios of A4/ dehydroepiandrosterone (DHEA), testosterone (Te)/DHEA, and greater ratios of E2/Te, and estrone/A4 were observed in sFF samples associated with LB. Among the oocytes associated with NP, in four out of 12 samples total concentration of androgens was above the distribution of the concentrations in the oocytes corresponding to the LB group. Observations of the study indicated increased consumption of precursors and increased biosynthesis of estrogens in the follicles associated with LB. Our data suggest that potentially steroid profiles in sFF obtained during oocyte retrieval may serve as biomarkers for selection of the best embryo to transfer after IVF.
ABSTRACT Mild (capillary) interface conditions which do not completely desolvate the ions of prot... more ABSTRACT Mild (capillary) interface conditions which do not completely desolvate the ions of proteins in electrospray ionization mass spectrometry (ESI-MS) may be required to probe the higher order structures and weak associations. For the small protein bovine ubiquitin, two ion distributions (unsolvated ions and unresolved solvated ions) were observed. The resolvable solvation for leucine-enkephalin with methanol and water shows that the use of countercurrent N{sub 2} flow at the capillary affects the solvation observed. 2 figs. (DLC)
To answer the questions: Are perinatal reproductive hormone profiles different in case of a twin ... more To answer the questions: Are perinatal reproductive hormone profiles different in case of a twin compared with a singleton pregnancy? Are reproductive endocrine profiles of twin girls influenced by their male co-twin and vice versa? Prospective cohort study from January 2004 to October 2009. Not applicable. A total of 204 mothers of twins and 248 singleton control subjects, aged >18 years, pregnant with a twin or singleton and no endocrine disease or malignancy. Blood samples were collected at mid-gestation from the mother and at delivery from the mothers and the umbilical cords. Estrogens, androgens, SHBG, progesterone, and gonadotropins were measured. Hormonal profiles were compared between singletons and twins, different types of twins, and opposite-sex and same-sex twins. Estrogen and progesterone concentrations were higher in mothers of twins compared with singletons, but twin babies had lower estrogen and progesterone concentrations at birth. Opposite-sex twin girls did not...
Mild (capillary) interface conditions which do not completely desolvate the ions of proteins in e... more Mild (capillary) interface conditions which do not completely desolvate the ions of proteins in electrospray ionization mass spectrometry (ESI-MS) may be required to probe the higher order structures and weak associations. For the small protein bovine ubiquitin, two ion distributions (unsolvated ions and unresolved solvated ions) were observed. The resolvable solvation for leucine-enkephalin with methanol and water shows that the use of countercurrent N{sub 2} flow at the capillary affects the solvation observed. 2 figs. (DLC)
Clinica chimica acta; international journal of clinical chemistry, Jan 2, 2015
Mass spectrometry coupled to liquid chromatography (LC-MS and LC-MS/MS) is an analytical techniqu... more Mass spectrometry coupled to liquid chromatography (LC-MS and LC-MS/MS) is an analytical technique that has rapidly grown in popularity in clinical practice. In contrast to traditional technology, mass spectrometry is superior in many respects including resolution, specificity, multiplex capability and has the ability to measure analytes in various matrices. Despite these advantages, LC-MS/MS remains high cost, labor intensive and has limited throughput. This specialized technology requires highly trained personnel and therefore has largely been limited to large institutions, academic organizations and reference laboratories. Advances in automation will be paramount to break through this bottleneck and increase its appeal for routine use. This article reviews these challenges, shares perspectives on essential features for LC-MS/MS total automation and proposes a step-wise and incremental approach to achieve total automation through reducing human intervention, increasing throughput ...
The technique of electrospray ionization (ESI) has significantly extended the ability to characte... more The technique of electrospray ionization (ESI) has significantly extended the ability to characterize large molecules by mass spectrometry. Proteins to at least 200,000 D can be transferred intact to the gas phase and molecular weights determined with precisions as high as 0.001% if individual charge states can be resolved. The ESI-MS can also serve as a near ideal interface and
Journal of The American Society for Mass Spectrometry, 2015
Mass spectrometry enables the study of increasingly larger biomolecules with increasingly higher ... more Mass spectrometry enables the study of increasingly larger biomolecules with increasingly higher resolution, which is able to distinguish between fine isotopic variants having the same additional nucleon count, but slightly different masses. Therefore, the analysis of the fine isotopic distribution becomes an interesting research topic with important practical applications. In this paper, we propose the comprehensive methodology for studying the basic characteristics of the fine isotopic distribution. Our approach uses a broad spectrum of methods ranging from generating functions-that allow us to estimate the variance and the information theory entropy of the distribution-to the theory of thermal energy fluctuations. Having characterized the variance, spread, shape, and size of the fine isotopic distribution, we are able to indicate limitations to high resolution mass spectrometry. Moreover, the analysis of "thermorelativistic" effects (i.e., mass uncertainty attributable to relativistic effects coupled with the statistical mechanical uncertainty of the energy of an isolated ion), in turn, gives us an estimate of impassable limits of isotopic resolution (understood as the ability to distinguish fine structure peaks), which can be moved further only by cooling the ions. The presented approach highlights the potential of theoretical analysis of the fine isotopic distribution, which allows modeling the data more accurately, aiming to support the successful experimental measurements. Graphical Abstract ᅟ.
Serum testosterone can be measured by LC-MS/MS and RIA. We investigated whether the testosterone-... more Serum testosterone can be measured by LC-MS/MS and RIA. We investigated whether the testosterone-fracture relationship was affected by the method of measurement. We measured total testosterone (TT) by LC-MS/MS (TTLC-MS/MS) and RIA (TTRIA) in serum samples collected from 602 men whose incident fractures had been continuously ascertained by x-ray reports from 1989 to 2010. We measured bone mineral density (BMD) by dual-energy x-ray absorptiometry. The association between TT and fracture risk was assessed by the Cox proportional hazards model, taking into account the effect of age and BMD. Mean TTLC-MS/MS was higher than TTRIA by 27 ng/dL (95% CI 13-41). The concordance correlation coefficient between TTLC-MS/MS and TTRIA was 0.72 (95% CI 0.68-0.76). The Deming regression equation linking the 2 measurements was ln(TTLC-MS/MS + 10) = 0.87 + 0.87 × ln(TTRIA + 10). The hazard ratio of fracture per SD decrease in TT was 1.32 (95% CI 1.12-1.54) for TTLC-MS/MS and 1.23 (1.06-1.43) for TTRIA....
Methods in molecular biology (Clifton, N.J.), 2013
Isotopic information determined by mass spectrometry can be used in a wide variety of application... more Isotopic information determined by mass spectrometry can be used in a wide variety of applications. Broadly speaking these could be classified as "passive" applications, meaning that they use naturally occurring isotopic information, and "active" applications, meaning that the isotopic distributions are manipulated in some way. The classic passive application is the determination of chemical composition by comparing observed isotopic patterns of molecules to theoretically calculated isotopic patterns. Active applications include isotope exchange experiments of a variety of types, as well as isotope labeling in tracing studies and to provide references for quantitation. Regardless of the type of application considered, the problem of theoretical calculation of isotopic patterns almost invariably arises. This paper reviews a number of application examples and computational approaches for isotopic studies in mass spectrometry.
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Papers by Alan Rockwood