22 research outputs found
Kinetic evidence for interaction of TMPyP4 with two different G-quadruplex conformations of human telomeric DNA
Background: Stabilization of G-quadruplex helices by small ligands has attracted growing attention because they
inhibit the activity of the enzyme telomerase, which is overexpressed in> 80% cancer cells. TMPyP4, one of the
most studied G-quadruplex ligands, is used as a model to show that the ligands can exhibit different binding
features with different conformations of a human telomeric specific sequence.
Methods: UVâVis, FRET melting Assay, Isothermal Titration Calorimetry, Time-resolved Fluorescence lifetime,
T-Jump and Molecular Dynamics.
Results: TMPyP4 yields two different complexes with two Tel22 telomeric conformations in the presence of Na+
or K+. T-Jump kinetic experiments show that the rates of formation and dissociation of these complexes in the
ms time scale differ by one order of magnitude. MD simulations reveal that, in K+ buffer, âhybrid 1â conformation
yields kinetic constants on interaction with TMPyP4 one order lower than âhybrid 2â. The binding
involves ÏâÏ stacking with external loop bases.
Conclusions: For the first time we show that for a particular buffer TMPyP4 interacts in a kinetically different
way with the two Tel22 conformations even if the complexes formed are thermodynamically indistinguishable.
General significance: G-quadruplexes, endowed with technological applications and potential impact on regulation
mechanisms, define a new research field. The possibility of building different conformations from same
sequence is a complex issue that confers G-quadruplexes very interesting features. The obtaining of reliable
kinetic data constitutes an efficient tool to determine reaction mechanisms between conformations and small
molecules.âla
Caixaâ Foundation (project OSLC-2012-007), MINECO, (CTQ2014-
58812-C2-2-R) and Junta de Castilla y LeĂłn, (BU042U16), FEDER
Funds Spai
Role of Seroalbumin in the Cytotoxicity of cis-Dichloro Pt(II) Complexes with (N^N)-Donor Ligands Bearing Functionalized Tails
Given the potent anticancer properties of cisdiamminedichloroplatinum(
II) and knowing its mode of action, we
synthesized four new cis-[PtCl2(N^N)] organoplatinum complexes, two
with N-substituted pbi ligands (pbiR = 1-R-2-(2-pyridyl)benzimidazole)
(namely, 1 and 2) and two more with 4,4âČ-disubstituted bpy ligands (bpy =
2,2âČ-bipyridine) (namely, 3 and 4). We explored their cytotoxicity and
ability to bind to deoxyguanosine monophosphate (dGMP), DNA, and
albumin models. By 1H NMR and UVâvis spectroscopies, circular
dichroism, agarose gel electrophoresis, differential scanning calorimetry
measurements, and density functional theory calculations, we verified that
only 3 can form aquacomplex species after dimethyl sulfoxide solvation;
surprisingly, 1, 2, and 3 can bind covalently to DNA, whereas 4 can form a noncovalent complex. Interestingly, only complexes 1
and 4 exhibit good cytotoxicity against human ovarian carcinoma (HeLa) cell line, whereas 2 and 3 are inactive. Although lung
carcinoma (A549) cells are more resistant to the four platinum complexes than HeLa cells, when the protein concentration in the
extracellular media is lower, the cytotoxicity becomes substantially enhanced. By native electrophoresis of bovine seroalbumin
(BSA) and inductively coupled plasma mass spectrometry uptake studies we bear out, on one hand, that 2 and 3 can interact
strongly with BSA and its cellular uptake is negligible and, on the other hand, that 1 and 4 can interact with BSA only weakly, its
cellular uptake being higher by several orders. These results point up the important role of the protein binding features on their
biological activity and cellular uptake of cis-âPtCl2â derivatives. Our results are valuable in the future rational design of new
platinum complexes with improved biological properties, as they expose the importance not only of their DNA binding abilities
but also of additional factors such as protein binding.La
Caixa Foundation (LCF/PR/PR12/11070003), Ministerio de
EconomiÌa
y Competitividad-FEDER (CTQ2014-58812-C2-2-
R, CTQ2014-58812-C2-1-R, and CTQ2015-70371-REDT),
ConsejeriÌa
de EducacioÌnâJunta de Castilla y LeoÌn-FEDER
(BU042U16), Spain
Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study
Summary
Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally.
Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies
have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of
the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income
countries globally, and identified factors associated with mortality.
Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to
hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis,
exomphalos, anorectal malformation, and Hirschsprungâs disease. Recruitment was of consecutive patients for a
minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical
status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary
intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause,
in-hospital mortality for all conditions combined and each condition individually, stratified by country income status.
We did a complete case analysis.
Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital
diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal
malformation, and 517 with Hirschsprungâs disease) from 264 hospitals (89 in high-income countries, 166 in middleincome
countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male.
Median gestational age at birth was 38 weeks (IQR 36â39) and median bodyweight at presentation was 2·8 kg (2·3â3·3).
Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income
countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups).
Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome
countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries;
pâ€0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients
combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88â4·11],
p<0·0001; middle-income vs high-income countries, 2·11 [1·59â2·79], p<0·0001), sepsis at presentation (1·20
[1·04â1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention
(ASA 4â5 vs ASA 1â2, 1·82 [1·40â2·35], p<0·0001; ASA 3 vs ASA 1â2, 1·58, [1·30â1·92], p<0·0001]), surgical safety
checklist not used (1·39 [1·02â1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed
(ventilation 1·96, [1·41â2·71], p=0·0001; parenteral nutrition 1·35, [1·05â1·74], p=0·018). Administration of
parenteral nutrition (0·61, [0·47â0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65
[0·50â0·86], p=0·0024) or percutaneous central line (0·69 [0·48â1·00], p=0·049) were associated with lower mortality.
Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome,
middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will
be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger
than 5 years by 2030