Cellular Redox Systems Impact the Aggregation of Cu,Zn Superoxide Dismutase Linked to Familial Amyotrophic Lateral Sclerosis.

Protein misfolding is implicated in neurodegenerative diseases such as ALS, where mutations of superoxide dismutase 1 (SOD1) account for about 20% of the inherited mutations. Human SOD1 (hSOD1) contains four cysteines, including Cys(57) and Cys(146), which have been linked to protein stability and folding via forming a disulfide bond, and Cys(6) and Cys(111) as free thiols. But the roles of the cellular oxidation-reduction (redox) environment in SOD1 folding and aggregation are not well understood.

Predictive urinary biomarkers for steroid-resistant and steroid-sensitive focal segmental glomerulosclerosis using high resolution mass spectrometry and multivariate statistical analysis.

Background: Focal segmental glomerulosclerosis (FSGS) is a glomerular scarring disease diagnosed mostly by kidney biopsy. Since there is currently no diagnostic test that can accurately predict steroid responsiveness in FSGS, prediction of the responsiveness of patients to steroid therapy with noninvasive means has become a critical issue. In the present study urinary proteomics was used as a noninvasive tool to discover potential predictive biomarkers.

Prognostic polypeptide blood plasma biomarkers of Alzheimer's disease progression.

Background: Patients with mild cognitive impairment (MCI) have varying risks of progression to Alzheimer's disease (AD).

Objective: To test the utility of the relative abundances of blood plasma polypeptides for predicting the risk of AD progression.

Methods: 119 blood plasma samples of patients with MCI with different outcomes (stable MCI and progressive MCI) were analyzed by untargeted, label-free shotgun proteomics.

Blood plasma IgG Fc glycans are significantly altered in Alzheimer's disease and progressive mild cognitive impairment.

Blood-based anti-amyloid-β (Aβ) immunoglobulins (IgGs) and peripheral inflammation are factors correlating with development of Alzheimer's disease (AD). IgG functionality can drastically change from anti- to pro-inflammatory via alterations in the IgG-Fc N-glycan structure. Herein, we tested if IgG-Fc glycosylation in plasma is indeed altered during the development of AD.

Shotgun brain proteomics reveals early molecular signature in presymptomatic mouse model of Alzheimer's disease.

AβpE3-42 (N-terminal truncated amyloid-β peptide starting with pyroglutamate at the third position) is abundant in Alzheimer's disease (AD) brain and has high aggregation propensity and cellular toxicity. Transgenic TBA42 mice expressing AβpE3-42 exhibit a neurological phenotype evident at the age of 12 months. As AD has a long presymptomatic period, early detection of imminent neurodegeneration is highly desirable.

Brain proteomics supports the role of glutamate metabolism and suggests other metabolic alterations in protein l-isoaspartyl methyltransferase (PIMT)-knockout mice.

Protein l-isoaspartyl methyltransferase (PIMT) repairs the isoaspartyl residues (isoAsp) that originate from asparagine deamidation and aspartic acid (Asp) isomerization to Asp residues. Deletion of the gene encoding PIMT in mice (Pcmt1) leads to isoAsp accumulation in all tissues measured, especially in the brain. These PIMT-knockout (PIMT-KO) mice have perturbed glutamate metabolism and die prematurely of epileptic seizures.

N-terminal peptide sequence repetition influences the kinetics of backbone fragmentation: a manifestation of the Jahn-Teller effect?

Analysis of large (>10,000 entries) databases consisting of high-resolution tandem mass spectra of peptide dications revealed with high statistical significance (P < 1[Symbol: see text]10(-3)) that peptides with non-identical first two N-terminal amino acids undergo cleavages of the second peptide bond at higher rates than repetitive sequences composed of the same amino acids (i.e., in general AB- and BA- bonds cleave more often than AA- and BB- bonds).

In silico instrumental response correction improves precision of label-free proteomics and accuracy of proteomics-based predictive models.

In the analysis of proteome changes arising during the early stages of a biological process (e.g. disease or drug treatment) or from the indirect influence of an important factor, the biological variations of interest are often small (∼10%).

Carbonyl charge solvation patterns may relate to fragmentation classes in collision-activated dissociation.

Here, we investigate the hypothesis that the origin of Class I fragmentation in tryptic peptide dications corresponding to the cleavage of the first two amino acids from the N-terminus is due to a dominant charge solvation pattern. Molecular dynamics simulations (MDS) of model A(n)R dications confirmed the existence of a persistent solvation of the protonated N-terminus on the second backbone carbonyl. Additionally, MDS predicted a new distinct fragmentation class corresponding to the loss of two amino acids from the C-terminus.

Introducing an Asp-Pro linker in the synthesis of random one-bead-one-compound hexapeptide libraries compatible with ESI-MS analysis.

A random hexapeptide library (one-bead-one-compound), containing sixteen amino acids (16(6) different sequences) was synthesized on a Tentagel resin previously modified with a dipeptide linker (Asp-Pro). This peptide bond is highly susceptible to cleavage under mild acidic conditions in a salt-free solution prepared with H(2)(16)O/H(2)(18)O (60/40% v/v). In the hydrolysis, hexapeptides are released with an additional Asp residue partially labeled with (18)O at the C-terminus.

Heme binding in gas-phase holo-myoglobin cations: distal becomes proximal?

His64 and His93 are the two well-known sites of heme binding in water-dissolved holo-myoglobin, with His93 being a proximal, strongly binding partner, while the distal His64 weakly coordinates to the heme through a small-molecule ligand, e.g., water or O(2).

Alzheimer's disease and mild cognitive impairment are associated with elevated levels of isoaspartyl residues in blood plasma proteins.

Increased levels of isoaspartyl residues (isoAsp) have previously been found in proteins of Alzheimer's disease (AD) brains and in blood proteins of patients suffering from uremia, the disease sharing common pathological features with AD. One can hypothesize that higher levels of isoAsp should be present in blood proteins of AD patients. Also, because of higher AD prevalence in females, they can be expected to have higher level of isoAsp than males.

New proteomic developments to analyze protein isomerization and their biological significance in plants.

Spontaneous isoaspartyl formation from aspartyl dehydration or asparaginyl deamidation is a major source of modifications in protein structures. In cells, these conformational changes could be reverted by the protein L-isoaspartyl methyltransferase (PIMT) repair enzyme that converts the isoaspartyl residues into aspartyl. The physiological importance of this metabolism has been recently illustrated in plants.

Calibration function for the Orbitrap FTMS accounting for the space charge effect.

Ion storage in an electrostatic trap has been implemented with the introduction of the Orbitrap Fourier transform mass spectrometer (FTMS), which demonstrates performance similar to high-field ion cyclotron resonance MS. High mass spectral characteristics resulted in rapid acceptance of the Orbitrap FTMS for Life Sciences applications. The basics of Orbitrap operation are well documented; however, like in any ion trap MS technology, its performance is limited by interactions between the ion clouds.

Mass spectrometric analysis of asparagine deamidation and aspartate isomerization in polypeptides.

One of the most frequent modifications in proteins and peptides is the deamidation of asparagine, a spontaneous non-enzymatic reaction leading to a mixture of L,D-succinimidyl, L,D-aspartyl, and L,D-isoaspartyl forms, with L-isoaspartyl dominating. Spontaneous isomerization of L-Asp yields the same products. In vivo, these unusual forms of aspartate are repaired by the protein L-isoaspartyl O-methyltransferase enzyme, with the balance between isomerization and repair affecting the organism physiology.

Toward proteome-scale identification and quantification of isoaspartyl residues in biological samples.

Deamidation of asparaginyl and isomerization of aspartyl residues in proteins produce a mixture of aspartyl and isoaspartyl residues, the latter being involved in protein aging and inactivation. Electron capture dissociation (ECD) combined with Fourier transform mass spectrometry (FT MS) are known to be able to distinguish the isoaspartyl peptides by unique fragments of cn* + 58.0054 (C2H2O2) and z(l-n)-56.

Evolution of a domain conserved in microtubule-associated proteins of eukaryotes.

The microtubule network, the major organelle of the eukaryotic cytoskeleton, is involved in cell division and differentiation but also with many other cellular functions. In plants, microtubules seem to be involved in the ordered deposition of cellulose microfibrils by a so far unknown mechanism. Microtubule-associated proteins (MAP) typically contain various domains targeting or binding proteins with different functions to microtubules.