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At least 19 recordsLinked to original sources
PubMed1999

Comparative mass spectrometric analyses of Photofrin oligomers by fast atom bombardment mass spectrometry, UV and IR matrix-assisted laser desorption/ionization mass spectrometry, electrospray ionization mass spectrometry and laser desorption/jet-cooling photoionization mass spectrometry.

Photofrin (porfimer sodium) is a porphyrin derivative used in the treatment of a variety of cancers by photodynamic therapy. This oligomer complex and a variety of porphyrin monomers, dimers and trimers were analyzed with five different mass spectral ionization techniques: fast atom bombardment, UV and IR matrix-assisted laser desorption/ionization, electrospray ionization, and laser desorption/jet-cooling photoionization. All five approaches resulted in very similar oligomer distributions with an average oligomer length of 2.7 +/- 0.1 porphyrin units. In addition to the Photofrin analysis, this study provides a side-by-side comparison of the spectra for the five different mass spectrometric techniques.

Dihematoporphyrin Ether↗
PubMed2003

Effect of instrument tuning on the detectabilityof biopolymers in electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry of multiply charged biopolymer ions of different molecular size revealed a strong influence of tuning parameters on their detectability in quadrupole ion trap and triple quadrupole mass spectrometers. Hence, after optimizing the ion optical parameters with the signal of the 4- charge state of (dT)(24) (low charge state tuning), a tenfold increase in the signal-to-noise ratio for a mixture of oligodeoxythymidylic acids (n = 12-18) was obtained compared with the results achieved with tune parameters optimized with a synthetic 80-mer oligodeoxynucleotide. By contrast, a detection limit in the upper femtomole region could only be reached for a 104-mer oligodeoxynucleotide utilizing the 24- charge state of the 80-mer (high charge state tuning). The same effect was observed for proteins investigated in the positive ion mode using low and high charge states of cytochrome c and carbonic anhydrase, respectively, for instrument tuning. By comparing the settings for low and high charge state tuning, it became obvious that the most significant difference was observed in the potential applied to the heated metal capillary used to transfer ions from the atmospheric pressure to the vacuum region of the ion source. Taking advantage of the optimized tuning procedure, the molecular mass of a 61 base pair product of polymerase chain reaction was accurately determined by electrospray ionization mass spectrometry on-line interfaced to ion-pair reversed-phase high-performance liquid chromatography.

Base Sequence↗
PubMed2005

Analysis of noncovalent complexes between human telomeric DNA and polyamides containing N-methylpyrrole and N-methylimidazole by using electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry (ESI-MS) was used to investigate noncovalent complexes formed between four novel polyamides containing N-methylpyrrole (Py) and N-methylimidazole (Im), and human telomeric DNA. Of the four polyamides investigated, PyPyPygammaImImImbetaDp (3) had the highest binding affinity towards the duplex d(TTAGGGTTAGGG/CCCTAACCCTAA) (D1). Results of competition analysis showed that the polyamides had binding affinities with D1 in the order PyPyPygammaImImImbetaDp (3)>PyPyPyPygammaPyImImPybetaDp (4)>PyPyPybetaImImImbetaDp (2)>>ImImImbetaDp (1). MS/MS spectra confirmed that binding between D1 and the hairpin polyamides is more stable than that with the three-ring polyamides. By contrast, in the case of single-stranded d(TTAGGGTTAGGG)(D2), the binding order changes to ImImImbetaDp (1)>PyPyPygammaImImImbetaDp (3)>PyPyPybetaImImImbetaDp (2).

DNA↗
PubMed2004

Metabolomic analysis of molecular species of phospholipids from normotensive and preeclamptic human placenta electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry (ESI/MS) is a highly sensitive, fast and powerful technique for the metabolite and metabolomic analysis of mixtures of lipids in a biological extract. We have exploited this technique to identify and characterize various phospholipids present in the placenta of preeclamptic and normal pregnant women. Multiple major molecular species can be detected in each phospholipid class have arachidonic acid as major fatty acid constituent. There is no remarkable difference in the molecular composition in each of these phospholipids in both the extracts. However, there seems to be lower amounts of the plasmenyl phosphatidylethanolamine and greater amounts of free fatty acids in preeclamptic placenta.

Arachidonic Acids↗
PubMed2003

Enzymatic strategies for the characterization of nucleic acids by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry (ESI-MS) is a powerful technique used for the identification and characterization of DNA polymorphisms. Continual improvement in instrument design assures high mass measurement accuracy, sensitivity, and resolving power. This work describes an eclectic array of enzymatic strategies we have invoked in order to detect single-nucleotide polymorphisms by ESI-MS, although other applications may be envisioned. One strategy combines the use of two enzymes, exonuclease III and lambda exonuclease, to provide a ladder of single-stranded DNA fragments for straightforward sequence identification by mass spectrometry. A second strategy combines restriction enzymes to screen for polymorphisms present within specific amplicons. Finally, we describe the use of stable-isotope-labeled nucleotides for the determination of length and base composition of a PCR product.

Exodeoxyribonucleases↗
PubMed2003

G-quadruplex formation of thrombin-binding aptamer detected by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry detected the formation of the G-quadruplex structure of the thrombin-binding aptamer, d(GGTTGGTGTGGTTGG), and established its specific interaction with metal ions. One piece of evidence that the bonding in the gas phase is via the G-quadruplex form is the enhanced binding, with respect to other metal ions, of the aptamer with Sr2+, Pb2+, Ba2+, and K+, which are of similar size. Another is the lack of specific binding with controls in which the G's are replaced with A's. The most convincing evidence is the extent of H/D exchange of the gas-phase aptamer as compared to that bound to K+ and Sr2+. The latter two complexes exchange six and nine fewer H's, indicating a significant increase in protection upon binding to the metals. Mass spectrometry will be an important tool in understanding G-quadruplexes, which are particularly important in DNA telomers.

DNA↗
PubMed2006

Investigation of structure, dynamics and function of metalloproteins with electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry (ESI MS) has emerged recently as a powerful tool for analyzing many structural and behavioral aspects of metalloproteins in great detail. In this review we discuss recent developments in the field, placing particular emphasis on the unique features of ESI MS that lend themselves to metalloprotein characterization at a variety of levels. Direct mass measurement enables the determination of protein-metal ion binding stoichiometry in solution and metalloprotein higher order structure in the case of multi-subunit proteins. MS techniques have been developed for determining the locations of metal-binding centers, metal oxidation states and reaction intermediates of metal-containing enzymes. Other ESI MS techniques are also discussed, such as protein ion charge state distributions and hydrogen/deuterium exchange studies, which can be used to measure metal binding affinities and to shed light on vital dynamic aspects of the functional properties of metalloproteins endowed by metal binding.

Binding Sites↗
PubMed2004

Evaluation of complexes of DNA duplexes and novel benzoxazoles or benzimidazoles by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry is used to compare the metal ion binding and metal-mediated DNA binding of benzoxazole (1, 2, 3, 4) and benzimidazole (5) compounds and to elucidate the putative binding modes and stoichiometries. The observed metal versus non-metal-mediated DNA binding, as well as the specificity of DNA binding, is correlated with the biological activities of the analogs. The ESI-MS spectra for the antibacterial benzoxazole and benzimidazole analogs 4 and 5 demonstrated non-specific and non-metal-mediated binding to DNA, with the appearance of DNA complexes containing multiple ligands. The anticancer analog 2 demonstrates a clear preference for metal-mediated DNA interactions, with an apparent selectivity for Ni2+ -mediated binding over the more physiologically relevant Mg2+ or Zn2+ cations. Complexation between DNA and the biologically inactive analog 1 was not observed, either in the absence or presence of metal cations.

Anti-Bacterial Agents↗
PubMed2001

Detection of noncovalent complex between alpha-amylase and its microbial inhibitor tendamistat by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry (ESI-MS) is now routinely used for detection of noncovalent complexes. However, detection of noncovalent protein-protein complexes is not a widespread practice and still produces some challenges for mass spectrometrists. Here we demonstrate the detection of a noncovalent protein-protein complex between alpha-amylase and its microbial inhibitor tendamistat using ESI-MS. Crude porcine pancreatic alpha-amylase was purified using a glycogen precipitation method. Noncovalent complexes between porcine pancreatic alpha-amylase and its microbial inhibitor tendamistat are probed and detected using ESI-MS. The atmosphere-vacuum ESI conditions along with solution conditions and the ratio of inhibitor over enzyme strongly affect the detection of noncovalent complexes in the gas phase. ESI mass spectra of alpha-amylase at pH 7 exhibited charge states significantly lower than that reported previously, which is indicative of a native protein conformation necessary to produce a noncovalent complex. Detection of noncovalent complexes in the gas phase suggests that further use of conventional biochemical approaches to provide a qualitative, and in some cases even quantitative, characterization of equilibria of noncovalent complexes in solution is possible.

Animals↗
PubMed2002

Uncoupled analysis of secondary and tertiary protein structure by circular dichroism and electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry (ESI-MS) applied to protein conformational studies is a powerful new method that seems to provide specific information about protein tertiary structure. In this study, we analyzed the effect of trifluoroethanol (TFE) on a myoglobin peptide and cytochrome c (cyt c) at low pH by circular dichroism (CD) and ESI-MS. These experiments show that coil-to-helix transition per se does not affect ESI mass spectra, confirming that this technique is insensitive to the local conformation of the polypeptidic chain and, rather, reports on the tertiary contacts characterizing different protein conformations. This property makes ESI-MS an excellent method, complementary to CD, for the characterization of protein conformational changes. Fluorinated alcohols have been suggested to induce molten globule formation in acid-unfolded cyt c. The experiments described here show that TFE does not induce major changes in the ESI mass spectrum of cyt c at pH 2.2, indicating that no stabilization of compact, globular structures is detectable under the conditions employed. On the other hand, even low concentrations of TFE (2-5%) are shown to destabilize the folded state of the protein around the mid-point of its acid-induced unfolding transition.

Animals↗
PubMed2005

Speciation of cyclo(Pro-Gly)3 and its divalent metal-ion complexes by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry (ESI-MS) was used to study the binding of selected group II and divalent transition-metal ions by cyclo(Pro-Gly)3 (CPG3), a model ion carrier peptide. Metal salts (CatXn) were combined with the peptide (M) at a molar ratio of 1:10 M/Cat in aqueous solvents containing 50% vol/vol acetonitrile or methanol and 1 or 10 mM ammonium acetate (NH4Ac). Species detected include [M+H]+, [M+Cat-H]+, [M2+Cat]2+, [M+Cat+Ac]+, and [M+Cat+X]+. The relative stabilities of complexes formed with different cations (Mg2+, Ca2+, Sr2+, Mn2+, Co2+, Ni2+, Cu2+, and Zn2+) were determined from the abundance of 1:1 and 2:1 M/Cat species relative to that of the unbound peptide. The largest metal ions (Ca2+, Sr2+, and Mn2+) formed the most stable complexes. Reducing the buffer concentration increased the overall extent of metal binding. Results show that the binding specificity of CPG3 depends upon the size of the metal ion and its propensity for electrostatic interaction with oxygen atoms. Product ion tandem mass spectrometry of [M+H]+ and [M+Cu-H]+ confirmed the cyclic structure of the peptide, although the initial site(s) of metal attachment could not be determined.

Binding Sites↗
PubMed2003

Complexation of silver and co-recovered metals with novel aza-crown ether macrocycles by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry (ESI-MS) is used to evaluate the metal binding selectivities of an array of novel caged macrocycles for silver, gold, copper, nickel, zinc, iron, lead, manganese and alkali metal ions. It is found that five of the new compounds display silver selectivity, and their relative affinities for various metals depend on the type, number, and arrangement of heteroatoms (N, O), the cavity size, and the presence of aromatic substituents. Alkali metal cation binding studies are used to evaluate the size-selectivities of the cavities of the macrocycles. Electronic structure calculation by B3LYP density function theory methods were used to model the metal complexes. The presence of nitrogen atoms in the macrocyclic ring is essential for silver selectivity over other transition metals and alkali metal ions, and the presence of aromatic groups also enhances silver avidity. Macrocycle 3, a triaza-18-crown-6 analog modified with two phenyl groups and a cage group, is capable of selective extraction of Ag+ from aqueous solutions in the presence of other transition metal ions and the most common alkali and alkaline earth metal ions.

Crown Ethers↗
PubMed2005

Identification of complexes containing glutathione with As(III), Sb(III), Cd(II), Hg(II), Tl(I), Pb(II) or Bi(III) by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry (ESI-MS) of mixtures containing glutathione (GSH) and nitrates, oxides or chlorides of the heavy metals, arsenic, antimony, cadmium, mercury, thallium, lead or bismuth allows for definitive identification of complexes in the gas phase. In the positive ion mode, spectra show prominent m/z peaks that are assigned to monocations of general formulae [E(GSH)-xH]+ (E = Cd, Hg, Tl, Pb, As, Sb or Bi; x = 0, 1 or 2), [E(GSH)2-xH]+ (E = Hg, As, Sb, or Bi; x = 1 or 2), [E(GSH)3-xH]+ (E = As, Sb or Bi; x = 2), [E2(GSH)-xH]+ (E = Tl or Pb; x = 1 or 3), [E2(GSH)2-xH]+ (E = Bi; x = 5), [E2(GSH)3-xH]+ (E = Bi; x = 5), and/or [E3(GSH)-xH]+ (E = Tl; x = 2). Spectra obtained in the negative ion mode give m/z peaks observed in assigned to monoanionic species that correspond to some of the monocationic species listed above with two protons removed. The results demonstrate the potential application of ESI-MS as a versatile and efficient approach to study toxic heavy metals in biological systems. In addition, the observations provide a foundation database to understand the chemistry of these heavy metals with bio-molecules.

Chlorides↗
PubMed2005

Quantitation of cardiolipin molecular species in spontaneously hypertensive heart failure rats using electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry has previously been used to probe qualitative changes in the phospholipid cardiolipin (CL), but it has rarely been used in a quantitative manner. We assessed changes in the amount of individual molecular species of cardiac CL present in a model of congestive heart failure using 1,1',2,2'-tetramyristoyl cardiolipin as an internal standard. There was a linear relationship between the ratio of the negative molecular ion ([M-H]-) current from four different CL reference standards and the [M-H]- from the internal standard, as a function of the concentration of CL molecular species. Therefore, this internal standard can be used to quantitate many naturally occurring CL molecular species over a wide range of CL concentrations. Using this method, changes to individual molecular species of CL in failing hearts from male spontaneously hypertensive heart failure rats were examined. CL isolated from cardiac mitochondria was compared with left ventricular tissue to demonstrate the feasibility of extracting and quantitating CL from either mitochondrial or tissue samples. The acyl chain composition of individual CL molecular species was identified using tandem mass spectrometry. In animals with heart failure, the major cardiac CL species (tetralinoloyl) decreased significantly, whereas other minor CL species were significantly increased.

Animals↗
PubMed2006

Evaluation of binding of perylene diimide and benzannulated perylene diimide ligands to DNA by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry (ESI-MS) and spectroscopic studies in solution were used to evaluate the self-association, G-quadruplex DNA binding, and selectivity of a series of perylene diimides (PDIs) (PIPER, Tel01, Tel11, Tel12, and Tel18) or benzannulated perylene diimide ligands (Tel34 and Tel32). Fluorescence and resonance light scattering spectra of Tel01, Tel12, Tel32, and Tel34 reveal that these analogs undergo self-association in solution. UV-Vis and fluorescence titrations with G-quadruplex, duplex, or single-stranded DNA demonstrate that all the analogs, with the exception of Tel32, bind to G-quadruplex DNA, with those PDIs that are self-associated in solution showing the highest degree of selectivity for binding G-quadruplex DNA. Parallel ESI-MS analysis of the stoichiometries demonstrates the ability of the ligands, with the exception of Tel32, to bind to G-quadruplex DNA. While most ligands show major 1:1 and 2:1 binding stoichiometries as expected in the case of end-stacking, interestingly, three of the most quadruplex-selective ligands show a different behavior. Tel01 forms 3:1 complexes, while Tel12 and Tel32 only form 1:1 complexes. Collisional activation dissociation patterns are compatible with ligand binding to G-quadruplex DNA via stacking on the ends of the terminal G-tetrads. Experiments with duplex and single strand DNA were performed to assess the binding selectivities of the ligands. PIPER, Tel11, and Tel18 demonstrated extensive complexation with duplex DNA, while Tel11 and Tel18 bound to single strand DNA, confirming the lack of selectivity of these two ligands. Our results indicate that Tel01, Tel12, and Tel34 are the most selective for G-quadruplex DNA.

Base Sequence↗
PubMedDate not supplied

Studying noncovalent protein complexes by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry has been used to study protein interactions driven by noncovalent forces. The gentleness of the electrospray ionization process allows intact protein complexes to be directly detected by mass spectrometry. Evidence from the growing body of literature suggests that the ESI-MS observations for these weakly bound systems reflect, to some extent, the nature of the interaction found in the condensed phase. Stoichiometry of the complex can be easily obtained from the resulting mass spectrum because the molecular weight of the complex is directly measured. For the study of protein interactions, ESI-MS is complementary to other biophysical methods, such as NMR and analytical ultracentrifugation. However, mass spectrometry offers advantages in speed and sensitivity. The experimental variables that play a role in the outcome of ESI-MS studies of noncovalently bound complexes are reviewed. Several applications of ESI-MS are discussed, including protein interactions with metal ions and nucleic acids and subunit protein structures (quaternary structure).

Ions↗
PubMed1997

Analysis of peptide synthesis products by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry is an easy, rapid method for the verification of proper peptide synthesis and for the identification of most synthetic by-products. A synthesis-purification scheme has been described that uses mass analysis to (1) confirm the presence of the proper product in the crude peptide mixture, (2) guide the purification process, and (3) confirm the mass and purity of the final product. Even though many of these steps could be performed just as well with other ionization techniques, the liquid-flow characteristics of electrospray source are clearly an advantage when LC-MS is required. In addition, the ease with which fragment ions can be generated to provide structural information, even with the least sophisticated instruments, is a further advantage of ESI-MS. Although much of the operation described here was done manually, many of the steps could be automated with little additional effort (e.g., use of an autosampler). Quadrupole and ion trap instruments are widely available at present and provide the chemist with a variety of instruments from which to choose. Electrospray time-of-flight instruments will be commercially have just become available and should also provide similar results. As electrospray instruments continue to evolve, the instruments display greater performance and enhanced user-friendly interfaces, yet are lower in price and smaller in size. These features should lead to even more widespread use for the characterization of synthetic peptides.

Mass Spectrometry↗
PubMed2003

Mechanistic studies of photochemical reactions with millisecond time resolution by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry is used as an on-line technique to investigate the solution photochemistry of [CpFebz]+ (Cp, eta5-cyclopentadienyl; bz, eta6-benzene). Direct irradiation of samples in the optically transparent tip of the electrospray source allows the detection of products with lifetimes down to the millisecond regime. Photolysis of [CpFebz]+ in acetonitrile (AN) yields the short-lived half-sandwich complex, [CpFe(AN)3]+. The suspected parent-offspring relationship between this species and the fully ring-deligated product, [Fe(AN)6]2+, has been confirmed. In solutions containing cyclohexene oxide, [CpFebz]+ generates several photoproducts capable of initiating the cationic polymerization of the epoxide monomer. The initiation process and the first few steps in the subsequent growth of the polymer chain have been observed.

Journal Article↗