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Daniel Schwartz

Publications and source records attributed to Daniel Schwartz.

12 recordsLinked to original sources
PubMed2006

Integrity and stability studies of precipitated rhBMP-2 microparticles with a focus on ATR-FTIR measurements.

A major obstacle in the development of protein drug formulations is the need to maintain the native, active protein structure both during the formulation process and upon long time storage. Controlled precipitation was evaluated for its potential to supply stable microparticulate formulations of bone-regenerating recombinant human Bone Morphogenetic Protein-2 (rhBMP-2). Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) did provide insight into the protein formulation and stability. Temperature dependent ATR-FTIR measurements and DSC measurements allow for the study of changes in the protein structure during melting. To address the question of isomerization, peptide mapping was performed, and protein aggregation was monitored by size exclusion chromatography (SEC). It could be demonstrated by ATR-FTIR that controlled precipitation did not harm the protein and the process is fully reversible. DSC measurements further confirmed these findings. No changes in the transition temperature and process were observed after precipitation and redissolution. Upon storage, isomerization and aggregation could be detected, but to a lower extent in the precipitated formulation as compared to a solution reference. Thus, controlled precipitation of rhBMP-2 is fully reversible and has the potential as alternative formulation tool for the generation of a microparticulate drug delivery system.

Bone Morphogenetic Protein 2↗
PubMed2006

Identification of 14-3-3epsilon substrates from embryonic murine brain.

Mice deficient in 14-3-3epsilon exhibit abnormal neuronal migration and die perinatally. We report here the first large-scale analysis of 14-3-3 interacting partners from primary animal tissue, identifying from embryonic murine brain 163 14-3-3epsilon interacting proteins and 85 phosphorylation sites on these proteins. Phosphorylation of the deubiquitinating enzyme USP8 at serine 680 was found essential for its interaction with 14-3-3epsilon and for maintaining USP8 in the cytosol.

14-3-3 Proteins↗
PubMed2005

An iterative statistical approach to the identification of protein phosphorylation motifs from large-scale data sets.

With the recent exponential increase in protein phosphorylation sites identified by mass spectrometry, a unique opportunity has arisen to understand the motifs surrounding such sites. Here we present an algorithm designed to extract motifs from large data sets of naturally occurring phosphorylation sites. The methodology relies on the intrinsic alignment of phospho-residues and the extraction of motifs through iterative comparison to a dynamic statistical background. Results show the identification of dozens of novel and known phosphorylation motifs from recently published serine, threonine and tyrosine phosphorylation studies. When applied to a linguistic data set to test the versatility of the approach, the algorithm successfully extracted hundreds of language motifs. This method, in addition to shedding light on the consensus sequences of identified and as yet unidentified kinases and modular protein domains, may also eventually be used as a tool to determine potential phosphorylation sites in proteins of interest.

Algorithms↗
PubMed2005

An in vivo MRI study of prefrontal cortical complexity in first-episode psychosis.

OBJECTIVE: The purpose of this study was to investigate abnormalities in the surface complexity of the prefrontal cortex and in the hemispheric asymmetry of cortical complexity in first-episode patients with schizophrenia. METHOD: An estimate of the surface complexity of the prefrontal cortex was derived from the number of voxels along the boundary between gray matter and CSF. Magnetic resonance imaging scans were acquired from patients with a first episode of schizophrenia (N=17), patients with a first episode of affective psychosis (N=17), and normal comparison subjects (N=17), age-matched within a narrow age range (18-29 years). This study group was the focus of a previous study that showed lower prefrontal cortical volume in patients with schizophrenia. RESULTS: Prefrontal cortical complexity was not significantly different among the groups. However, the schizophrenia patients differed significantly from the normal comparison subjects in asymmetry, with the schizophrenia patients showing less left-greater-than-right asymmetry in cortical complexity than the comparison subjects. CONCLUSIONS: An abnormal pattern of asymmetry in the prefrontal cortex of first-episode patients with schizophrenia provides evidence for a neurodevelopmental mechanism in the etiology of schizophrenia.

Adolescent↗
PubMed2004

Phosphoproteomic analysis of the developing mouse brain.

Proper development of the mammalian brain requires the precise integration of numerous temporally and spatially regulated stimuli. Many of these signals transduce their cues via the reversible phosphorylation of downstream effector molecules. Neuronal stimuli acting in concert have the potential of generating enormous arrays of regulatory phosphoproteins. Toward the global profiling of phosphoproteins in the developing brain, we report here the use of a mass spectrometry-based methodology permitting the first proteomic-scale phosphorylation site analysis of primary animal tissue, identifying over 500 protein phosphorylation sites in the developing mouse brain.

Amino Acid Sequence↗
PubMed2004

Large-scale characterization of HeLa cell nuclear phosphoproteins.

Determining the site of a regulatory phosphorylation event is often essential for elucidating specific kinase-substrate relationships, providing a handle for understanding essential signaling pathways and ultimately allowing insights into numerous disease pathologies. Despite intense research efforts to elucidate mechanisms of protein phosphorylation regulation, efficient, large-scale identification and characterization of phosphorylation sites remains an unsolved problem. In this report we describe an application of existing technology for the isolation and identification of phosphorylation sites. By using a strategy based on strong cation exchange chromatography, phosphopeptides were enriched from the nuclear fraction of HeLa cell lysate. From 967 proteins, 2,002 phosphorylation sites were determined by tandem MS. This unprecedented large collection of sites permitted a detailed accounting of known and unknown kinase motifs and substrates.

Amino Acid Sequence↗
PubMed2003

CHIP-Hsc70 complex ubiquitinates phosphorylated tau and enhances cell survival.

The microtubule-binding protein tau has been implicated in the neurofibrillary pathology of Alzheimer's disease. Within affected cells, ubiquitinated and hyperphosphorylated tau assembles into massive filamentous polymers. Eventually these tangle-bearing neurons die. The formation of neurofibrillary tangles closely parallels the progression and anatomic distribution of neuronal loss in Alzheimer's disease, suggesting that these lesions play a role in the disease pathogenesis. Mutations in the human tau gene cause autosomal dominant neurodegenerative disorders. These and other neurodegenerative conditions are also characterized by extensive neurofibrillary pathology. The mechanisms underlying tau-mediated neurotoxicity remain unclear; however, phosphorylated tau is a strong candidate for a toxic molecule, particularly those isoforms phosphorylated by the kinases glycogen synthase kinase 3beta and Cdk5. Here we show that Alzheimer tau binds to Hsc70, and its phosphorylation is a recognition requirement for the addition of ubiquitin (Ub) by the E3 Ub ligase CHIP (carboxyl terminus of the Hsc70-interacting protein) and the E2 conjugating enzyme UbcH5B. Other E3 Ub ligases including parkin and Cbl failed to ubiquitinate phosphorylated tau. CHIP could rescue phosphorylated tau-induced cell death, and therefore the CHIP-Hsc70 complex may provide a new therapeutic target for the tauopathies.

Animals↗
PubMed2003

Multimodality monitoring of transcranial electric motor and somatosensory-evoked potentials during surgical correction of spinal deformity in patients with cerebral palsy and other neuromuscular disorders.

STUDY DESIGN: This prospective, descriptive study determined the reliability of transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials in children with neuromuscular scoliosis. OBJECTIVE: To assess the applicability of transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials during surgical correction of neuromuscular scoliosis, particularly with cerebral palsy-related deformity. SUMMARY OF BACKGROUND DATA: During corrective spinal surgery for neuromuscular scoliosis, intraoperative multimodality spinal cord monitoring is recommended. There exist conflicting, retrospective studies regarding the reliability of spinal cord monitoring in patients with neuromuscular scoliosis. METHODS: Transcranial electric motor potentials and posterior tibial nerve somatosensory-evoked potentials were monitored in all patients presenting for spinal fusion between 2000 and 2001. Anesthesia was standardized for all patients. RESULTS: There were 68 patients subdivided into two subject groups. Group I consisted of 39 patients with neuromuscular scoliosis associated with cerebral palsy, and Group II consisted of 29 children with neuromuscular scoliosis due to a disease process other than cerebral palsy. Five of the 68 patients had significant amplitude changes in 1 or both monitoring methods during surgery relative to baseline. Of these, one had permanent neurologic deficit despite standard intervention. Somatosensory-evoked potentials were monitored successfully in 82% of the cerebral palsy and 86% of the noncerebral palsy patients. Transcranial electric motor-evoked potentials, on the other hand, were monitorable in 63% of patients with mild or moderate degrees of cerebral palsy and 39% of those with severe involvement. Eighty-six percent of those with noncerebral palsy-related neuromuscular scoliosis had recordable motor-evoked potentials at baseline. CONCLUSION: Both transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials can be monitored reliably in most patients with neuromuscular scoliosis. Those with severe cerebral palsy present the greatest challenge to successful neurophysiologic monitoring.

Adolescent↗
PubMed2003

A proteomics approach to understanding protein ubiquitination.

There is a growing need for techniques that can identify and characterize protein modifications on a large or global scale. We report here a proteomics approach to enrich, recover, and identify ubiquitin conjugates from Saccharomyces cerevisiae lysate. Ubiquitin conjugates from a strain expressing 6xHis-tagged ubiquitin were isolated, proteolyzed with trypsin and analyzed by multidimensional liquid chromatography coupled with tandem mass spectrometry (LC/LC-MS/MS) for amino acid sequence determination. We identified 1,075 proteins from the sample. In addition, we detected 110 precise ubiquitination sites present in 72 ubiquitin-protein conjugates. Finally, ubiquitin itself was found to be modified at seven lysine residues providing evidence for unexpected diversity in polyubiquitin chain topology in vivo. The methodology described here provides a general tool for the large-scale analysis and characterization of protein ubiquitination.

Amino Acid Sequence↗
PubMed2002

The canine minute virus (minute virus of canines) is a distinct parvovirus that is most similar to bovine parvovirus.

We characterized the genome and proteins of the canine minute virus (the minute virus of canines (MVC)). The genome sequence showed MVC to be an autonomous parvovirus encoding a large nonstructural protein 1 gene, a smaller nonstructural protein, and overlapping VP1 and VP2 protein genes. The virus was most closely related to bovine parvovirus (BPV), with which it was 43% identical at the DNA sequence level, while the NS1 and VP1 proteins were 33.6 and 41.4% identical to those of BPV, respectively. Spliced messages of the NS1 gene transcripts were detected by RT-PCR. VP1 and VP2 proteins were detected in purified capsids, as were modified versions of each protein, and VP3 was also found in full capsids.

Amino Acid Sequence↗
PubMed2002

Risk of recurrent stroke in children with sickle cell disease receiving blood transfusion therapy for at least five years after initial stroke.

OBJECTIVE: To test the hypothesis that children with sickle cell disease (SCD) who have an initial stroke temporally unrelated to another medical event are at higher risk for recurrent stroke than are children who had strokes temporally related to medical events. METHODS: A retrospective cohort study of children with SCD and stroke who received regularly scheduled blood transfusions for a minimum of 5 years was conducted. Medical records were examined for the documentation of antecedent or concurrent medical events (hypertension, acute chest syndrome, aplastic crisis, fever associated with infection, exchange transfusion) associated with physician contact within 14 days before the initial stroke. RESULTS: A total of 137 pediatric patients from 14 centers were studied. Mean age at first stroke was 6.3 years (1.4 to 14.0 years) with mean follow-up of 10.1 years (5 to 24 years). Thirty-one (22%) patients had a second stroke (2.2 per 100 patient years); 26 patients had an identified medical or concurrent event associated with their initial stroke. None of these patients had recurrent stroke 2 or more years after the initial event. The remaining 111 patients had an ongoing risk of recurrent stroke (1.9 per 100 patient-years) despite long-term transfusions (P =.038). CONCLUSIONS: The absence of an antecedent or concurrent medical event associated with an initial stroke is a major risk factor for subsequent stroke while receiving regular transfusions.

Adolescent↗