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1.
Int J Cardiol ; 393: 131379, 2023 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-37734491

RESUMO

BACKGROUND: Approximately 20-30% of patients with a cardiac disease suffer from anxiety and/or depression, leading to poor health outcomes. To identify this subgroup, clinical guidelines recommend screening for anxiety and depression in cardiac rehabilitation (CR). It is unknown how screening practice is delivered post-COVID. METHODS: This observational study used data from the National Audit of Cardiac Rehabilitation from April 2018-March 2022. Descriptive statistics were used to assess screening rates and prevalence, while a multivariate logistic regression model was performed to analyse determinants for screening for anxiety and depression among patients participating in cardiac rehabilitation. RESULTS: The population consisted of 245,705 patients, where 128,643 (52.4%) were screened and 117,062 (47.6%) were not. Patients attending CR during first year of COVID-19 were less likely to be screened. Patients with female gender, living alone, non-white ethnicity, living in the most deprived areas, current smoking, and physical inactivity were less likely to be screened, while patients who were revascularized, having an objective physical fitness test, and attending a certified CR center were more likely to be screened. For patients attending CR during COVID-19, the prevalence of anxiety and depression decreased significantly. For anxiety the prevalence dropped from 34.4% to 15.8%, for depression the prevalence dropped from 33.5% to 16.5%. CONCLUSION: CR service provision was negatively impacted during COVID-19, leading to much lower screening for anxiety and depression in the CR setting. Prevalence of anxiety and depression decreased during COVID-19 for this population, possibly because psychologically affected patients refrained from attending CR.

2.
Dermatol Online J ; 29(1)2023 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-37040910

RESUMO

Lymphomatoid papulosis is a chronic CD30-positive cutaneous lymphoproliferative disorder that is characterized by recurring red-brown necrotic papules. It exhibits a wide spectrum of histopathologic findings and is often associated with cutaneous T-cell lymphomas. Six different histological subtypes have been classified by the WHO, but there is limited understanding regarding rare histopathologic variants. We describe a 51-year-old man who presented with recurring, necrotic papules for 6 years that progressed to involve the face, scalp, trunk, axilla, and scrotum. Histopathology demonstrated sarcoidal granulomas, along with a CD30-positive T cell infiltrate which demonstrated clonality by T cell receptor gamma gene rearrangement. A diagnosis of lymphomatoid papulosis associated with granulomas was established based on the clinical and histopathologic presentation. The clinical understanding of granulomatous lymphomatoid papulosis is limited in the available literature and more awareness of this histopathologic variant is required for accurate classification of this disorder.


Assuntos
Exantema , Papulose Linfomatoide , Neoplasias Cutâneas , Masculino , Humanos , Pessoa de Meia-Idade , Papulose Linfomatoide/patologia , Antígeno Ki-1 , Recidiva Local de Neoplasia/patologia , Pele/patologia , Neoplasias Cutâneas/patologia , Exantema/patologia
4.
Int J Cardiol ; 352: 65-71, 2022 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-35143875

RESUMO

BACKGROUND: Anxiety and depression are prevalent in 20% of patients with acute coronary syndrome (ACS) and associated with poor outcomes. Guidelines recommend screening for these conditions in cardiac rehabilitation (CR) however, clinical practice is inconsistent. Sparse knowledge exists on determinants for screening. METHODS: This observational study used data from the National Audit of Cardiac Rehabilitation from January 2016-December 2019. A multivariate logistic regression model was performed to analyze patient- and provider level determinants for screening for anxiety and depression among patients with ACS. RESULTS: The population consisted of 138,018 patients, where 82,507 (59.8%) were screened and 55,511 (40.2%) were not. Younger age, non-white ethnicity, living in areas of social deprivation, current smoking, body mass index>30, and physical activity<150 min per week were negatively correlated with patients being screened. Compared to patients having a percutaneous coronary intervention, patients undergoing coronary artery bypass grafting or medical treatment were less likely to be screened. History of anxiety, depression, osteoporosis, chronic back problems, and asthma were positively correlated with screening, while chronic obstructive pulmonary disease, diabetes, hypertension, and stroke were negatively correlated with screening. Regarding provider level, certification of CR centers was positively associated with screening, while looking over time data showed an incremental negative trend in screening from 2016 to 2019. CONCLUSION: We found both patient and provider level determinants of screening for anxiety and depression. Clinical practice is still inconsistent especially for high-risk groups. We recommend systematic screening to enable tailored interventions which in turn may mitigate inequity in health outcomes.


Assuntos
Reabilitação Cardíaca , Ansiedade/diagnóstico , Ansiedade/epidemiologia , Transtornos de Ansiedade , Ponte de Artéria Coronária , Depressão/diagnóstico , Depressão/epidemiologia , Depressão/terapia , Humanos
6.
J Intensive Care Soc ; 19(4): 313-318, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30505345

RESUMO

Acute kidney injury is common in critically ill patients, with ultrasound recommended to exclude renal tract obstruction. Intensive care unit clinicians are skilled in acquiring and interpreting ultrasound examinations. Intensive Care Medicine Trainees wish to learn renal tract ultrasound. We sought to demonstrate that intensive care unit clinicians can competently perform renal tract ultrasound on critically ill patients. Thirty patients with acute kidney injury were scanned by two intensive care unit physicians using a standard intensive care unit ultrasound machine. The archived images were reviewed by a Radiologist for adequacy and diagnostic quality. In 28 of 30 patients both kidneys were identified. Adequate archived images of both kidneys each in two planes were possible in 23 of 30 patients. The commonest reason for failure was dressings and drains from abdominal surgery. Only one patient had hydronephrosis. Our results suggest that intensive care unit clinicians can provide focussed renal tract ultrasound. The low incidence of hydronephrosis has implications for delivering the Core Ultrasound in Intensive Care competencies.

7.
Eur J Prev Cardiol ; 25(18): 1925-1933, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30188178

RESUMO

AIMS: Cardiac rehabilitation is one of the most cost-effective interventions for patients with cardiovascular disease. Worldwide supervised group-based cardiac rehabilitation is the dominant mode of delivery followed by facilitated self-managed (FSM), which is emerging as part of a cardiac rehabilitation menu. Modern research evidence, using trials and well-resourced interventions, suggests FSM is comparable to supervised rehabilitation in its outcomes for patients; however, this is yet to be established using routine clinical practice data. METHODS: Including 81,626 patients from routine clinical data in the National Audit of Cardiac Rehabilitation, this observational study investigated whether mode of delivery, supervised or FSM, was associated with similar cardiac rehabilitation outcomes. Hierarchical regression models included patient and service covariates such as age, gender, cardiac rehabilitation duration and programme staff type. RESULTS: The results showed 85% of the population received supervised cardiac rehabilitation. The FSM group were significantly older, female and predominantly in lower socioeconomic groups. The results showed that all patients on average benefit from cardiac rehabilitation, independently of mode of delivery, across all risk factors. Additional benefit of 13% and 11.4% increased likelihood of achieving the target state for physical activity and body mass index respectively when using FSM approaches. CONCLUSION: This is the first study to investigate traditional cardiovascular risk factors with cardiac rehabilitation mode of delivery using routine clinical data. Both modes of delivery were associated with comparable statistically significant positive outcomes. Despite having equivalent outcomes, FSM cardiac rehabilitation continues to be underutilised, with less than 20% of patients receiving this mode of delivery in the UK.


Assuntos
Reabilitação Cardíaca/métodos , Doenças Cardiovasculares/terapia , Atenção à Saúde/métodos , Prevenção Secundária/métodos , Autocuidado/métodos , Idoso , Pressão Sanguínea , Índice de Massa Corporal , Doenças Cardiovasculares/diagnóstico , Doenças Cardiovasculares/fisiopatologia , Comorbidade , Exercício Físico , Feminino , Nível de Saúde , Estilo de Vida Saudável , Humanos , Masculino , Pessoa de Meia-Idade , Medição de Risco , Fatores de Risco , Fatores Sexuais , Abandono do Hábito de Fumar , Fatores Socioeconômicos , Resultado do Tratamento
8.
J Am Soc Mass Spectrom ; 27(3): 487-97, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26602904

RESUMO

A detailed energy-resolved study of the fragmentation reactions of protonated histidine-containing peptides and their b2 ions has been undertaken. Density functional theory calculations were utilized to predict how the fragmentation reactions occur so that we might discern why the mass spectra demonstrated particular energy dependencies. We compare our results to the current literature and to synthetic b2 ion standards. We show that the position of the His residue does affect the identity of the subsequent b2 ion (diketopiperazine versus oxazolone versus lactam) and that energy-resolved CID can distinguish these isomeric products based on their fragmentation energetics. The histidine side chain facilitates every major transformation except trans-cis isomerization of the first amide bond, a necessary prerequisite to diketopiperazine b2 ion formation. Despite this lack of catalyzation, trans-cis isomerization is predicted to be facile. Concomitantly, the subsequent amide bond cleavage reaction is rate-limiting.


Assuntos
Dicetopiperazinas/química , Histidina/análogos & derivados , Lactamas/química , Oxazolona/química , Peptídeos/química , Dipeptídeos/química , Isomerismo , Modelos Moleculares , Prótons , Espectrometria de Massas por Ionização por Electrospray
9.
J Am Soc Mass Spectrom ; 23(12): 2055-8, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-22996293

RESUMO

Middle-sized b(n) (n ≥ 5) fragments of protonated peptides undergo selective complex formation with ammonia under experimental conditions typically used to probe hydrogen-deuterium exchange in Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Other usual peptide fragments like y, a, a*, etc., and small b(n) (n ≤ 4) fragments do not form stable ammonia adducts. We propose that complex formation of b(n) ions with ammonia is characteristic to macrocyclic isomers of these fragments. Experiments on a protonated cyclic peptide and N-terminal acetylated peptides fully support this hypothesis; the protonated cyclic peptide does form ammonia adducts while linear b(n) ions of acetylated peptides do not undergo complexation. Density functional theory (DFT) calculations on the proton-bound dimers of all-Ala b(4), b(5), and b(7) ions and ammonia indicate that the ionizing proton initially located on the peptide fragment transfers to ammonia upon adduct formation. The ammonium ion is then solvated by N(+)-H…O H-bonds; this stabilization is much stronger for macrocyclic b(n) isomers due to the stable cage-like structure formed and entropy effects. The present study demonstrates that gas-phase guest-host chemistry can be used to selectively probe structural features (i.e., macrocyclic or linear) of fragments of protonated peptides. Stable ammonia adducts of b(9), b(9)-A, and b(9)-2A of A(8)YA, and b(13) of A(20)YVFL are observed indicating that even these large b-type ions form macrocyclic structures.


Assuntos
Peptídeos/química , Medição da Troca de Deutério , Gases/química , Íons/química , Compostos Macrocíclicos/química , Espectrometria de Massas , Modelos Moleculares
10.
J Am Soc Mass Spectrom ; 23(4): 594-601, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21952775

RESUMO

A detailed study has been made of the b(5) and a(5) ions derived from the amides H-Ala-Ala-Ala-Ala-Pro-NH(2), H-Ala-Ala-Ala-Pro-Ala-NH(2), and H-Ala-Ala-Pro-Ala-Ala-NH(2). From quasi-MS(3) experiments it is shown that the product ion mass spectra of the three b(5) ions are essentially identical, indicating macrocyclization/reopening to produce a common mixture of intermediates prior to fragmentation. This is in agreement with numerous recent studies of sequence scrambling in b ions. By contrast, the product ion mass spectra for the a(5) ions show substantial differences, indicating significant differences in the mixture of structures undergoing fragmentation for these three species. The results are interpreted in terms of a mixture of classical substituted iminium ions as well as protonated C-terminal amides formed by cyclization/rearrangement as reported recently for a(4) ions (Bythell, Maître , Paizs, J . Am. Chem. Soc. 2010, 132, 14761-14779). Novel fragment ions observed upon fragmentation of the a(5) ions are protonated H-Pro-NH(2) and H-Pro-Ala-NH(2) which arise by fragmentation of the amides. The observation of these products provides strong experimental evidence for the cyclization/rearrangement reaction to form amides and shows that it also applies to a(5) ions.


Assuntos
Oligopeptídeos/química , Peptídeos/química , Prolina/química , Alanina/química , Íons/química , Espectrometria de Massas por Ionização por Electrospray , Espectrometria de Massas em Tandem
11.
J Am Soc Mass Spectrom ; 22(5): 906-11, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21472525

RESUMO

The product ion mass spectra resulting from collisional activation of doubly-protonated tryptic-type peptides Ala-Ala-Xaa-Ala-Ala-Ala-Arg have been determined for Xaa = Ala(A), Ser(S), Val(V), Thr(T), Ile(I), Phe(F), Tyr(Y), Sar, Met(M), Trp(W), Pro(P), and Gln(Q). The major fragmentation reaction involves cleavage of the second amide bond (counting from the N-terminus) except for Xaa = Ser and Thr where elimination of H(2)O from the [M + 2H](+2) ion forms the base peak. In general, the extent of cleavage of the second amide bond shows little dependence on the identity of Xaa and little dependence on whether the bond cleavage involves symmetrical bond cleavage to form a y(5)/b(2) ion pair or asymmetrically to form y (5) (+2) and a neutral b(2) species. Notable exceptions to this generalization occur for Xaa equal to Pro or Sar. For Xaa = Pro only cleavage of the second amide bond is observed, consistent with a pronounced proline effect, i.e., cleavage N-terminal to Pro. When Xaa = Sar considerably enhanced cleavage of the second amide bond also is observed, suggesting that at least part of the proline effect relates to the tertiary nature of the amide nitrogen. In the competition between symmetric and asymmetric bond cleavage an attempt to establish a linear free energy correlation in relating ln(y(5)(+2)/y(5)) to PA(H-Xaa-OH) did not lead to a reasonable correlation although the trend of increasing y(5)(+2)/y(5) ratio with increasing proton affinity of H-Xaa-OH was clear. Proline showed a unique behavior in giving a much higher y(5)(+2)/y(5) ratio than any of the other residues studied.


Assuntos
Aminoácidos/química , Fragmentos de Peptídeos/química , Espectrometria de Massas por Ionização por Electrospray/métodos , Sequência de Aminoácidos , Peptídeos/química , Prolina/química , Tripsina/química
12.
J Am Soc Mass Spectrom ; 21(8): 1352-63, 2010 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-20541953

RESUMO

The MS(n) spectra of the [M + H](+) and b(5) peaks derived from the peptides HAAAAA, AHAAAA, AAHAAA, AAAHAA, and AAAAHA have been measured, as have the spectra of the b(4) ions derived from the first four peptides. The MS(2) spectra of the [M + H](+) ions show a substantial series of b(n) ions with enhanced cleavage at the amide bond C-terminal to His and substantial cleavage at the amide bond N-terminal to His (when there are at least two residues N-terminal to the His residue). There is compelling experimental and theoretical evidence for formation of nondirect sequence ions via cyclization/reopening chemistry in the CID spectra of the b ions when the His residue is near the C-terminus. The experimental evidence is less clear for ions when the His residue is near the N-terminus, although this may be due to the use of multiple alanine residues in the peptide making identifying scrambled peaks more difficult. The product ion mass spectra of the b(4) and b(5) ions from these isomeric peptides with cyclically permuted amino acid sequences are similar, but also show clear differences. This indicates less active cyclization/reopening followed by fragmentation of common structures for b(n) ions containing His than for sequences of solely aliphatic residues. Despite more energetically favorable cyclization barriers for the b(5) structures, the b(4) ions experimental data show more clear evidence of cyclization and sequence scrambling before fragmentation. For both b(4) and b(5) the energetically most favored structure is a macrocyclic isomer protonated at the His side chain.


Assuntos
Histidina/química , Peptídeos/química , Ciclização , Íons/química , Isomerismo , Espectrometria de Massas em Tandem/métodos , Termodinâmica
13.
J Am Soc Mass Spectrom ; 20(12): 2248-53, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19781958

RESUMO

The product ion mass spectra obtained by CID of the b(9) ions derived by loss of neutral alanine from the MH+ ion of the peptides Tyr(Ala)9, (Ala)4Tyr(Ala)5, and (Ala)8TyrAla are essentially identical, indicative of full cyclization reaction to a common intermediate before fragmentation. This leads to abundant nondirect sequence ions in the product ion mass spectra of the b9 ions. The product ion mass spectra of the b8 ions from the first two peptides also are essentially identical. The fragmentation of the MH+ ions also leads to low intensity nondirect sequence ions in the product ion mass spectra. N-terminal acetylation blocks the cyclization and eliminates nondirect sequence fragment ions in the product ion mass spectra.


Assuntos
Mapeamento de Peptídeos/métodos , Peptídeos/análise , Peptídeos/química , Espectrometria de Massas por Ionização por Electrospray/métodos , Íons
14.
Mass Spectrom Rev ; 28(4): 640-54, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19338048

RESUMO

Modern soft ionization techniques readily produce protonated or multiply protonated peptides. Collision-induced dissociation (CID) of these protonated species is often used as a method to obtain sequence information. In many cases fragmentation occurs at amide bonds. When the charge resides on the C-terminal fragment so-called y ions are produced which are known to be protonated amino acids or truncated peptides. When the charge resides on the N-terminal fragment so-called b ions are produced. Often the sequence of y and b ions are essential for peptide sequencing. The b ions have many possible structures, a knowledge of which is useful in this sequencing. The structures of b ions are reviewed in the following with particular emphasis on the variation of structure with the number of amino acid residues in the b ion and the effect of peptide side chain on b ion structure. The recent discovery of full cyclization of larger b ions results in challenges in peptide sequencing. This aspect is discussed in detail.


Assuntos
Íons/química , Oxazolona/química , Peptídeos/química , Espectrometria de Massas por Ionização por Electrospray/métodos , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz/métodos , Ciclização , Modelos Moleculares , Estrutura Molecular , Prótons
15.
Rapid Commun Mass Spectrom ; 23(9): 1298-302, 2009 May.
Artigo em Inglês | MEDLINE | ID: mdl-19306282

RESUMO

The fragmentation reactions of b3 ions of nominal structure AAAoxa, YAAoxa, AYAoxa and AAYoxa have been studied as a function of collision energy, allowing the construction of breakdown graphs expressing in a qualitative way the energy dependence of the fragmentation reactions. The primary fragmentation reactions of the AAAoxa b3 ion involve formation of the a3* (a3-NH3) ion and the b2 ion, with the latter becoming the dominant product at higher internal energies. For both YAAoxa and AYAoxa b3 ions the pathway to a3* is relatively minor with formation of b2 the dominant primary fragmentation reaction. For the AAYoxa b3 ion, in addition to a3*, abundant formation of the tyrosine (Y) iminium ion is observed with only minor formation of the b2 ion. The results support and expand upon the detailed mechanism of fragmentation of b3 ions proposed by Cooper et al. (J. Am. Soc. Mass Spectrom. 2006; 17: 1654).


Assuntos
Íons/química , Peptídeos/química , Espectrometria de Massas por Ionização por Electrospray/métodos , Peptídeos/análise , Termodinâmica
16.
J Am Chem Soc ; 128(32): 10364-5, 2006 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-16895391

RESUMO

Collision-induced dissociation (CID) of protonated YAGFL-NH2 leads to nondirect sequence fragment ions that cannot directly be derived from the primary peptide structure. Experimental and theoretical evidence indicate that primary fragmentation of the intact peptide leads to the linear YAGFLoxa b5 ion with a C-terminal oxazolone ring that is attacked by the N-terminal amino group to induce formation of a cyclic peptide b5 isomer. The latter can undergo various proton transfer reactions and opens up to form something other than the YAGFLoxa linear b5 isomer, leading to scrambling of sequence information in the CID of protonated YAGFL-NH2.


Assuntos
Peptídeos/química , Peptídeos/metabolismo , Sequência de Aminoácidos , Espectrometria de Massas , Dados de Sequência Molecular
17.
J Mass Spectrom ; 40(9): 1173-86, 2005 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-16041740

RESUMO

The collision-induced dissociation (CID) fragmentation reactions of a variety of deprotonated peptides containing proline have been studied in detail using MS(2) and MS(3) experiments, deuterium labelling and accurate mass measurements when necessary. The [M--H--CO(2)](-) (a(2)) ion derived from H-Pro-Xxx-OH dipeptides shows an unusual fragmentation involving loss of C(2)H(4); this fragmentation reaction is not observed for larger peptides. The primary fragmentation reactions of deprotonated tripeptides with an N-terminal proline are formation of a(3) and y(1) ions. When proline is in the central position of tripeptides, a(3), y(2) and y(1) ions are the primary fragmentation products of [M--H](-), while when the proline is in the C-terminal position, a(3)and y(1) ions are the major primary products. In the latter case, the a(3) ion fragments primarily to the ''b(2) ion; further evidence is presented that the ''b(2) ions have a deprotonated oxazolone structure. Larger deprotonated peptides having at least two amino acid residues N-terminal to proline show a distinct preference for cleavage of the amide bond N-terminal to proline to form, mainly, the appropriate y ion. This proline effect is compared and contrasted with the similar proline effect observed in the fragmentation of protonated peptides containing proline.


Assuntos
Peptídeos/química , Prolina/química , Espectrometria de Massas por Ionização por Electrospray/métodos , Prótons
18.
J Mass Spectrom ; 39(6): 647-54, 2004 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-15236303

RESUMO

N-Methylaniline (NMA) was ethylated and N-ethylaniline (NEA) was methylated under chemical ionization conditions using C(2)H(5)I and CH(3)I, respectively, as reagent gases. The structures of the resulting m/z 136 adduct ions have been probed using metastable ion and collision-induced dissociation (CID) methods. From the similarity of the spectra obtained and from the presence of structure-diagnostic ions at m/z 59 (CH(3)NHC(2)H(5) (+*)) and m/z 44 (CH(3)NHCH(2) (+)), it is concluded that predominantly N-alkylation occurs in both systems. This interpretation was aided by the use of C(2)D(5)I and CD(3)I as reagents. Adduct ions of m/z 136 were also formed by ethylation of the isomeric toluidines and by methylation of the ring-ethylanilines. The resulting CID mass spectra were distinctly different from those obtained for the m/z 136 ions obtained by alkylation of NMA and NEA. Protonation of N-ethyl-N-methylaniline using CH(3)C(==O)CH(3) as Brønsted acid reagent produced an m/z 136 species whose CID mass spectrum also featured intense ion signals at m/z 59 and 44. This observation led to the conclusion that protonation with acetone as reagent results, in this case, in dominant N-protonation. However, the CID mass spectrum of the m/z 136 ion formed when CH(3)OH was the protonating agent featured a weak signal at m/z 44 and no signal at m/z 59. Hence it was concluded that the latter m/z 136 ion contains a larger contribution from the ring-protonated adduct.

19.
J Am Soc Mass Spectrom ; 15(4): 446-56, 2004 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15047050

RESUMO

The fragmentation reactions of deprotonated N-benzoyl peptides, specifically hippurylglycine, hippurylglyclyclycine, and hippurylphenylalanine (hippuryl = N-benzoylGly) have been studied using MS2 and MS3 experiments as well as deuterium labeling. A major fragment ion is observed at m/z 160 ([C9H6NO2]-) which, upon collisional activation, mainly eliminates CO2 indicating that the two oxygen atoms have become bonded to the same carbon. This observation is rationalized in terms of formation of deprotonated 2-phenyl-5-oxazolone. Various pathways to the deprotonated oxazolone have been elucidated through MS3 experiments. Fragmentation of deprotonated N-acetylalanylalanine gives a relatively weak signal at m/z 112 which, upon collisional activation, fragments, in part, by loss of CO2 leading to the conclusion that the m/z 112 ion is deprotonated 2,4-dimethyl-5-oxazolone.


Assuntos
Glicina/análogos & derivados , Oxazolona/química , Fragmentos de Peptídeos/química , Peptídeos/química , Glicina/química , Espectrometria de Massas , Estrutura Molecular , Prótons
20.
Rapid Commun Mass Spectrom ; 17(8): 869-75, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-12672143

RESUMO

The fragmentation reactions of the [M-H](-) ions of the tripeptides H-Gly-Leu-Sar-OH, H-Leu-Gly-Pro-OH and H-Gly-Leu-Gly-OH have been investigated in detail using energy-resolved mass spectrometry, isotopic labelling and MS(3) experiments. It is shown that the major route to the "b(2) ions involves loss of a neutral amine from the a(3) ([M-H-CO(2)](-)) ion rather than being formed directly by fragmentation of the [M-H](-) ion. When there is no C-terminal amidic hydrogen (Sar, Pro), loss of a neutral amine is the dominant primary fragmentation reaction of the a(3) ion. However, when there is a C-terminal amidic hydrogen (Gly), elimination of the N-terminal amino acid residue is the major fragmentation reaction of the a(3) ion and formation of the "b(2) ion is greatly reduced in importance. It is proposed that the "b(2) ions are deprotonated oxazolones.


Assuntos
Amidas/química , Peptídeos/química , Sequência de Aminoácidos , Íons/química , Espectrometria de Massas , Estrutura Molecular , Prótons
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