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  1. Article ; Online: Managing nonspecific adsorption to liquid chromatography hardware: A review.

    Guimaraes, Guilherme J / Bartlett, Michael G

    Analytica chimica acta

    2023  Volume 1250, Page(s) 340994

    Abstract: The choice of alternative materials over stainless steel hardware in the construction of liquid chromatography systems has unveiled the degree to which nonspecific adsorption impacts the reproducibility of LC methods. Some of the major contributors to ... ...

    Abstract The choice of alternative materials over stainless steel hardware in the construction of liquid chromatography systems has unveiled the degree to which nonspecific adsorption impacts the reproducibility of LC methods. Some of the major contributors to nonspecific adsorption losses are charged metallic surfaces and leached metallic impurities, that may interact with the analyte and result in analyte loss and overall poor chromatographic performance. In this review, we describe several mitigation strategies available to chromatographers to minimize nonspecific adsorption to chromatographic systems. Alternative surfaces to stainless steel such as titanium, PEEK, and hybrid surface technologies are discussed. Furthermore, mobile phase additives used to prevent metal ion-analyte interactions are reviewed. Nonspecific adsorption of analytes is not reserved to metallic surfaces, as analytes may adsorb to the surfaces of filters, tubes, and pipette tips during sample preparation. Identifying the source of nonspecific interactions is paramount, as mitigation strategies may differ depending on what stage nonspecific losses are taking place. With this in mind, we discuss diagnostic methods that may help the chromatographer to differentiate losses resulting from sample preparation, and losses during LC runs.
    Language English
    Publishing date 2023-02-18
    Publishing country Netherlands
    Document type Journal Article ; Review
    ZDB-ID 1483436-4
    ISSN 1873-4324 ; 0003-2670
    ISSN (online) 1873-4324
    ISSN 0003-2670
    DOI 10.1016/j.aca.2023.340994
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  2. Article ; Online: Characterization of mRNA therapeutics.

    Guimaraes, Guilherme J / Kim, Jaeah / Bartlett, Michael G

    Mass spectrometry reviews

    2023  

    Abstract: Therapeutic messenger RNAs (mRNAs) have emerged as powerful tools in the treatment of complex diseases, especially for conditions that lack efficacious treatment. The successful application of this modality can be attributed to its ability to encode ... ...

    Abstract Therapeutic messenger RNAs (mRNAs) have emerged as powerful tools in the treatment of complex diseases, especially for conditions that lack efficacious treatment. The successful application of this modality can be attributed to its ability to encode entire proteins. While the large nature of these molecules has supported their success as therapeutics, its extended size creates several analytical challenges. To further support therapeutic mRNA development and its deployment in clinical trials, appropriate methods to support their characterization must be developed. In this review, we describe current analytical methods that have been used in the characterization of RNA quality, identity, and integrity. Advantages and limitations from several analytical techniques ranging from gel electrophoresis to liquid chromatography-mass spectrometry and from shotgun sequencing to intact mass measurements are discussed. We comprehensively describe the application of analytical methods in the measurements of capping efficiency, poly A tail analysis, as well as their applicability in stability studies.
    Language English
    Publishing date 2023-07-04
    Publishing country United States
    Document type Journal Article ; Review
    ZDB-ID 1491946-1
    ISSN 1098-2787 ; 0277-7037
    ISSN (online) 1098-2787
    ISSN 0277-7037
    DOI 10.1002/mas.21856
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  3. Article ; Online: Microflow liquid chromatography - multi-emitter nanoelectrospray mass spectrometry of oligonucleotides.

    Guimaraes, Guilherme J / Leach, Franklin E / Bartlett, Michael G

    Journal of chromatography. A

    2023  Volume 1696, Page(s) 463976

    Abstract: While the most sensitive LC-MS methods for oligonucleotide analysis contain ion-pairs in the mobile phase, these modifiers have been associated with instrument contamination and ion suppression. Typically, entire LC-MS systems are reserved for ... ...

    Abstract While the most sensitive LC-MS methods for oligonucleotide analysis contain ion-pairs in the mobile phase, these modifiers have been associated with instrument contamination and ion suppression. Typically, entire LC-MS systems are reserved for oligonucleotide LC-MS when using ion-pairing buffers. To overcome these limitations, numerous HILIC methods, liberated from ion-pairs, have been recently developed. Since ion-pairs play a role in analyte desorption from ESI droplets, their removal from mobile phases tend to impact method sensitivity. An effective way to recover MS sensitivity is to reduce the LC flow rate and therefore reduce ESI droplet size. With a focus on MS sensitivity, this study investigates the applicability of a microflow LC- nanoelectrospray MS platform in oligonucleotide ion-pair RP and HILIC LC-MS methods. The platform is effective and substantially increased the MS sensitivity of HILIC methods. Furthermore, LC method development for both types of separations provide insight into microflow chromatography of oligonucleotides, an under investigated chromatographic scale.
    MeSH term(s) Oligonucleotides/analysis ; Spectrometry, Mass, Electrospray Ionization/methods ; Chromatography, Liquid/methods ; Indicators and Reagents
    Chemical Substances Oligonucleotides ; Indicators and Reagents
    Language English
    Publishing date 2023-04-06
    Publishing country Netherlands
    Document type Journal Article
    ZDB-ID 1171488-8
    ISSN 1873-3778 ; 0021-9673
    ISSN (online) 1873-3778
    ISSN 0021-9673
    DOI 10.1016/j.chroma.2023.463976
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    Zs.A 813: Show issues Location:
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  4. Article: The critical role of mobile phase pH in the performance of oligonucleotide ion-pair liquid chromatography-mass spectrometry methods.

    Guimaraes, Guilherme J / Bartlett, Michael G

    Future science OA

    2021  Volume 7, Issue 10, Page(s) FSO753

    Language English
    Publishing date 2021-10-22
    Publishing country England
    Document type Journal Article
    ISSN 2056-5623
    ISSN 2056-5623
    DOI 10.2144/fsoa-2021-0084
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  5. Article ; Online: Mobile Phase Aging and Its Impact on Electrospray Ionization of Oligonucleotides.

    Guimaraes, Guilherme J / Saad, Jack G / Annavarapu, Vidya / Bartlett, Michael G

    Journal of the American Society for Mass Spectrometry

    2023  Volume 34, Issue 12, Page(s) 2691–2699

    Abstract: The implementation of fluoroalcohol/alkylamine mobile phase systems in oligonucleotide LC-MS provides a good balance between chromatographic separations and MS sensitivity. Since its introduction, several parameters including mobile phase composition, ... ...

    Abstract The implementation of fluoroalcohol/alkylamine mobile phase systems in oligonucleotide LC-MS provides a good balance between chromatographic separations and MS sensitivity. Since its introduction, several parameters including mobile phase composition, additive concentration, alkylamine hydrophobicity, and different fluoroalcohols have been carefully evaluated and optimized. While our understanding of this mobile phase system has increased over the years, there are challenges that continue to hinder method performance and remain poorly understood. One of these challenges is the constant loss of MS sensitivity over time, commonly termed mobile phase aging. This study investigates two aging mechanisms associated with loss of MS sensitivity: alkylamine oxidation and aggregate formation. The relationship between pH, organic solvent, oxygen, and mobile phase aging is characterized, and mitigation strategies to extend mobile phase lifetime are discussed.
    MeSH term(s) Oligonucleotides/chemistry ; Spectrometry, Mass, Electrospray Ionization/methods ; Chromatography, Liquid/methods ; Indicators and Reagents ; Solvents
    Chemical Substances Oligonucleotides ; Indicators and Reagents ; Solvents
    Language English
    Publishing date 2023-11-18
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1073671-2
    ISSN 1879-1123 ; 1044-0305
    ISSN (online) 1879-1123
    ISSN 1044-0305
    DOI 10.1021/jasms.3c00264
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    Zs.A 4618: Show issues Location:
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    Zs.MO 241: Show issues

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  6. Article ; Online: Consents (and Contents) Under Pressure: Maintaining Space for Moral Engagement in Research Protocols.

    Bartlett, Virginia L / Bliton, Mark J / Finder, Stuart G

    The American journal of bioethics : AJOB

    2022  Volume 22, Issue 3, Page(s) 68–70

    MeSH term(s) Humans ; Informed Consent ; Morals ; Stress, Psychological
    Language English
    Publishing date 2022-02-25
    Publishing country United States
    Document type Journal Article ; Comment
    ZDB-ID 2060433-6
    ISSN 1536-0075 ; 1526-5161
    ISSN (online) 1536-0075
    ISSN 1526-5161
    DOI 10.1080/15265161.2022.2027560
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    Zs.A 6814: Show issues Location:
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  7. Article ; Online: Modeling cationic adduction of oligonucleotides using electrospray desorption ionization.

    Sutton, J Michael / Bartlett, Michael G

    Rapid communications in mass spectrometry : RCM

    2020  Volume 34, Issue 8, Page(s) e8696

    Abstract: Rationale: Cationic adduction causes poor sensitivity and increases spectral complexity during mass spectral analysis of oligonucleotides and alkylamines are used to reduce this adduction. It is unclear the effect of the physiochemical properties of the ...

    Abstract Rationale: Cationic adduction causes poor sensitivity and increases spectral complexity during mass spectral analysis of oligonucleotides and alkylamines are used to reduce this adduction. It is unclear the effect of the physiochemical properties of the alkylamines on the reduction of the cationic adduction.
    Methods: All samples were directly infused into a Synapt G2 HDMS quadrupole time-of-flight (TOF) hybrid mass spectrometer in negative ion electrospray ionization mode through the native built-in fluidics system. The infusion flow rate was set to 50 μL/min. The TOFMS tuning parameters were as follows: capillary voltage -2.0 kV, cone voltage 25 V, extraction cone voltage 2 V, source temperature 125°C, desolvation temperature 450°C, cone gas flow rate 0 L/h, and desolvation gas (nitrogen) flow rate 1000 L/h.
    Results: A quantitative model was created to predict the optimized alkylamine for MS analysis, while a qualitative model was generated to explain the most important physiochemical properties: proton affinity (13.83%), gas-phase basicity (11.79%), pKa (11.47%), boiling point (10.73%), MW (10.3%), Henry's Law Constant (9.56%), and partition coefficient (logP) (9.44%). The quantitative model was applied to RNA (microRNA) and a phosphorothioate and predicts the trend of cationic adduction.
    Conclusions: Two models are described to understand the physiochemical properties that contribute to the adduction and to provide users a quick mathematical tool to predict the best choice of alkylamine to lower cationic adduction and decrease spectral complexity while enhancing sensitivity.
    MeSH term(s) Alkylation ; Amines/chemistry ; Cations/chemistry ; MicroRNAs/chemistry ; Models, Chemical ; Oligonucleotides/chemistry ; Protons ; Spectrometry, Mass, Electrospray Ionization
    Chemical Substances Amines ; Cations ; MicroRNAs ; Oligonucleotides ; Protons
    Language English
    Publishing date 2020-02-03
    Publishing country England
    Document type Journal Article
    ZDB-ID 58731-x
    ISSN 1097-0231 ; 0951-4198
    ISSN (online) 1097-0231
    ISSN 0951-4198
    DOI 10.1002/rcm.8696
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    Zs.A 3461: Show issues Location:
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  8. Book ; Online: On the functional form of the radial acceleration relation

    Desmond, Harry / Bartlett, Deaglan J. / Ferreira, Pedro G.

    2023  

    Abstract: ... data, we find the best functions typically satisfy $g_\text{obs} \propto g_\text{bar}$ at high $g_\text ... _\text{obs} \propto \sqrt{g_\text{bar}}$ as $g_\text{bar} \to 0$ is little evident at all. By generating ... the centripetal acceleration due to baryons, $g_\text{bar}$, to the total dynamical acceleration, $g_\text{obs ...

    Abstract We apply a new method for learning equations from data -- Exhaustive Symbolic Regression (ESR) -- to late-type galaxy dynamics as encapsulated in the radial acceleration relation (RAR). Relating the centripetal acceleration due to baryons, $g_\text{bar}$, to the total dynamical acceleration, $g_\text{obs}$, the RAR has been claimed to manifest a new law of nature due to its regularity and tightness, in agreement with Modified Newtonian Dynamics (MOND). Fits to this relation have been restricted by prior expectations to particular functional forms, while ESR affords an exhaustive and nearly prior-free search through functional parameter space to identify the equations optimally trading accuracy with simplicity. Working with the SPARC data, we find the best functions typically satisfy $g_\text{obs} \propto g_\text{bar}$ at high $g_\text{bar}$, although the coefficient of proportionality is not clearly unity and the deep-MOND limit $g_\text{obs} \propto \sqrt{g_\text{bar}}$ as $g_\text{bar} \to 0$ is little evident at all. By generating mock data according to MOND with or without the external field effect, we find that symbolic regression would not be expected to identify the generating function or reconstruct successfully the asymptotic slopes. We conclude that the limited dynamical range and significant uncertainties of the SPARC RAR preclude a definitive statement of its functional form, and hence that this data alone can neither demonstrate nor rule out law-like gravitational behaviour.

    Comment: 12+4 pages, 4 figures, 3 tables; minor revision to match MNRAS published version
    Keywords Astrophysics - Astrophysics of Galaxies ; Astrophysics - Cosmology and Nongalactic Astrophysics ; Astrophysics - Instrumentation and Methods for Astrophysics ; Computer Science - Machine Learning
    Publishing date 2023-01-11
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  9. Book ; Online: Priors for symbolic regression

    Bartlett, Deaglan J. / Desmond, Harry / Ferreira, Pedro G.

    2023  

    Abstract: When choosing between competing symbolic models for a data set, a human will naturally prefer the "simpler" expression or the one which more closely resembles equations previously seen in a similar context. This suggests a non-uniform prior on functions, ...

    Abstract When choosing between competing symbolic models for a data set, a human will naturally prefer the "simpler" expression or the one which more closely resembles equations previously seen in a similar context. This suggests a non-uniform prior on functions, which is, however, rarely considered within a symbolic regression (SR) framework. In this paper we develop methods to incorporate detailed prior information on both functions and their parameters into SR. Our prior on the structure of a function is based on a $n$-gram language model, which is sensitive to the arrangement of operators relative to one another in addition to the frequency of occurrence of each operator. We also develop a formalism based on the Fractional Bayes Factor to treat numerical parameter priors in such a way that models may be fairly compared though the Bayesian evidence, and explicitly compare Bayesian, Minimum Description Length and heuristic methods for model selection. We demonstrate the performance of our priors relative to literature standards on benchmarks and a real-world dataset from the field of cosmology.

    Comment: 8+2 pages, 2 figures. Accepted for The Genetic and Evolutionary Computation Conference (GECCO) 2023 Workshop on Symbolic Regression
    Keywords Computer Science - Machine Learning ; Astrophysics - Cosmology and Nongalactic Astrophysics ; Astrophysics - Instrumentation and Methods for Astrophysics
    Subject code 310
    Publishing date 2023-04-13
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  10. Book: A - G, tropics in general ; H - J, South Asia and Oceania

    Bartlett, Harley H

    (Fire in relation to primitive agriculture and grazing in the tropics ; : annotated bibliography / Harley H. Bartlett ; Vol. 2)

    1957  

    Institution University of Michigan / Department of Botany
    Series title Fire in relation to primitive agriculture and grazing in the tropics
    : annotated bibliography / Harley H. Bartlett ; Vol. 2
    Language English
    Size 873 S.
    Publisher Univ. of Michigan, Dep. of Botany
    Publishing place Ann Arbor
    Document type Book
    Database Former special subject collection: coastal and deep sea fishing

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