High-order structure and dissociation of gaseous peptide aggregates that are hidden in mass spectra

Injected-ion mobility and high-pressure ion mobility techniques have been used to examine the conformations of bradykinin, insulin chain A, and several other peptide ions in the gas phase. Under the experimental conditions employed, evidence for multimer formation in the mass spectra of peptides is minimal or absent altogether. However, ion mobility distributions show that aggregates of peptides (containing a single charge per monomer unit) are observed at the same mass-to-charge ratios as the singly charged parent ions. Collision cross sections for these clusters show that they have tightly packed roughly spherical conformations. We have bracketed the average density as 0.87 < p < 1.00 g cm-3. In some cases, specific stable aggregate forms within a cluster size can be distinguished indicating that some high order structures are favored in the gas phase. Multimer formation between different sizes of polyalanine peptides shows no evidence for size specificity in aggregate formation. Collisional and thermal excitation studies have been used to examine structural transitions and dissociation of the multimers. Aggregates appear to dissociate via loss of singly charged monomers. The observation that peptide multimers can be concealed in mass spectral data requires that fragmentation patterns and reactivity studies of singly charged monomers be undertaken with care.     

Fracture resistance of endodontically treated roots after restoration

This study evaluated the shear strength resistance of endodontically treated roots that were restored by two different techniques. Twenty-seven recently extracted single-rooted teeth with similar anatomic characteristics were sectioned to obtain the same length for all specimens. Group I (GI) consisted of 14 roots restored with cast post-core (nickel-chromium alloy) and cemented using zinc phosphate cement; group II (GII) consisted of 13 roots restored with steel prefabricated posts (FKG) cemented with zinc phosphate cement and rotated with caution for anchorage. The crown portion of this group was made using a hybrid composite resin (Prisma APH). Results showed that on all specimens of GI the fracture occurred in the cervical root structure while in GII the composite resin fractured in all specimens. Statistical analysis showed a significantly higher resistance to fracture for GI than GII. The specimens were sectioned longitudinally for stereoscopic microscope analysis (63x) and did not show fracture lines in the dentin anchorage post area for any of the specimens.     

Penicillin-binding proteins and induction of AmpC beta-lactamase

In competition assays for radiolabeled penicillin, penicillin-binding proteins (PBPs) 4, 7a, and 7b showed very high affinities for strong inducers of AmpC beta-lactamase. Loss of PBP 4 resulted in diminished inducibility. This suggests that if PBPs are involved in induction of AmpC beta-lactamase, there is probably a redundancy in function among the different PBPs.     

Suicide in head and neck cancer patients

PURPOSE: It has been well documented that patients with a diagnosis of cancer are at an increased risk of committing suicide. However, there is a paucity of literature on the risk of suicide in the head and neck cancer patient. The purpose of this investigation was to determine the incidence of suicide and expressed suicidal intent in a series of such cancer patients. PATIENTS AND METHODS: A retrospective chart review of 241 patients who were diagnosed with head and neck cancer at the University of Maryland Oral and Maxillofacial Surgery Oncology Division was done. RESULTS: Three patients were identified who committed suicide, 1.2% of the series. Two patients expressed suicidal intent, and four patients refused all treatment and counseling, preferring to die of their disease. CONCLUSIONS: Head and neck cancer patients have many of the same risk factors for suicide as patients with other forms of cancer. To reduce this risk, it is essential that the surgeon maintain good rapport with the patient, because this serves as a foundation for all other aspects of their therapy. In addition, these patients need to be fully evaluated for depression, hopelessness, pain, and other factors important in raising the possibility of suicide, and appropriate, aggressive management must be provided.     

Overexpression of glucagon-like peptide-1 receptor in an insulin-secreting cell line enhances glucose responsiveness

Pituitary adenylate cyclase-activating polypeptide (PACAP), a member of the VIP (vasoactive intestinal polypeptide) family of peptides, has been demonstrated in neurons of the sensory system. PACAP expression of these neurons is sensitive to nerve damages such as nerve crush or axotomy. In the present study, PACAP expression in the mesencephalic trigeminal nucleus of the rat was examined after transsection of the main trunk of the masseteric nerve. The primary sensory neurons of the nucleus are considered to have purely proprioceptive functions. By quantitative in situ hybridization using a PACAP [35S]cRNA probe, an increase in PACAP mRNA was observed on the side ipsilateral to transsection already after 3 h and the expression reached a peak 24 h after surgery after which the levels gradually decreased during the next 14 days. A low and constant expression of PACAP mRNA could be seen on the side contralateral to transsection. PACAP immunoreactivity was demonstrated on the ipsilateral side after 18 h, using a specific monoclonal PACAP antibody. Co-existence of PACAP with NPY and galanin was demonstrated 7 days after transsection. Analysis of the masseteric nerve by radioimmunoassay on transsected and normal nerve stumps revealed an increase of PACAP-38 immunoreactivity in the nerve proximal to the transsection compared to the normal side (15.3 vs. 6.1 pmol/g wt). The results suggest that PACAP has a role in the early phase of adaptation to nerve injury in the proprioceptive neurons.     

On the determination of polarization observables in proton-induced reactions using large-acceptance magnetic spectrometers

For proton-induced reactions, a formalism is presented to determine polarization observables using a focal-plane polarimeter in combination with a large-acceptance spectrometer, where also the effect of the scattering in the non-dispersive plane of the spectrometer is taken into account. The inclusive proton-carbon analyzing power needed for the determination of spin observables was studied over a wide angular range and a new parameterization for this quantity was deduced.     

Phage diabody repertoires for selection of large numbers of bispecific antibody fragments

Methods for the generation of large numbers of different bispecific antibodies are presented. Cloning strategies are detailed to create repertoires of bispecific diabody molecules with variability on one or both of the antigen binding sites. This diabody format, when combined with the power of phage display technology, allows the generation and analysis of thousands of different bispecific molecules. Selection for binding presumably also selects for more stable diabodies. Phage diabody libraries enable screening or selection of the best combination bispecific molecule with regards to affinity of binding, epitope recognition and pairing before manufacture of the best candidate.