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L Mazzarella

Publications and source records attributed to L Mazzarella.

12 recordsLinked to original sources
PubMed1992

Solid-state conformations of aminosuccinyl peptides: structure of tert-butyloxycarbonyl-L-prolyl-L-aminosuccinyl-glycyl-L-alanine methyl ester (Boc-L-Pro-L-Asu-Gly-L-Ala-OMe). A case of pseudo-translational symmetry.

C20H30N4O8, M(r) = 454.48, monoclinic, P2(1), a = 13.411 (2), b = 12.592 (2), c = 14.710 (1) A, beta = 104.30 (1) degrees, V = 2407 (6) A3, Z = 4, Dx = 1.254 Mg m-3, lambda (Cu K alpha) = 1.5418 A, mu = 0.783 mm-1, F(000) = 968, room temperature, final R = 0.086, wR = 0.080 for 4055 observed reflections. The title compound is a model for the intermediate formed in the deamidation reaction of porcine adrenocorticotropin hormone. The structure presents a pseudo-translational symmetry and was solved by using a modified version of the SIR88 package. In the refinement, few stereochemical restraints were needed to handle the static disorder shown by the C-terminal fragment of one molecule in the asymmetric unit. The conformation of the two independent molecules is almost identical and is a II' beta-bend, stabilized by an intramolecular hydrogen bond. In the crystal, screw-related molecules are linked by hydrogen bonds. The two molecules in the independent unit are related by the translation vector u = 0.4962 (2)a + 0.7310 (2)b + 0.5075 (2)c.

Amino Acid Sequence↗
PubMed1992

Histopathology of spontaneous brain herniations into the middle ear.

Two patients with spontaneous brain herniation into the middle ear have been operated on with a combined otoneurological approach. In case No. 1, two 2 x 3 mm arachnoid tissue herniations were found in the tegmen antri of the left ear. Six years later, a 8 x 9 mm mass consisting of prolapsed brain was removed from the right ear. The histological examination showed normal but disorganized nervous tissue. The surface consisted of middle ear mucosa or modified glial cells. More deeply numerous well preserved neurons and synapses were observed. In case No. 2, a 2 x 1 cm herniation was found in contact with the ossicles and the bony walls of the middle ear. The herniation consisted of partly degenerated nervous tissue which could explain the episode of temporal lobe seizure the patient experienced 8 years before surgery. In the world literature during the last 40 years, 29 cases of spontaneous or idiopathic brain herniation into the middle ear and mastoid have been reported. In 10, the herniations were multiple, as in our case No. 1. Case No. 1 is interesting also because the spontaneous brain herniation was bilateral.

Cerebrospinal Fluid Otorrhea↗
PubMed1992

[Desmoid tumors of the abdominal wall].

The authors report their experience in the management of desmoid tumors, rare benign neoplasias, locally aggressive and potentially recurrent after surgery. Etiopathogenetic, diagnostic, and therapeutic features of these tumors are analysed and the value of surgery as well as chemo- or radiotherapy is considered.

Abdominal Muscles↗
PubMed1979

Treatment of osteoradionecrosis by transoral hemimandibulectomy: report of case.

A case of progressive osteoradionecrosis after cobalt-60 radiation has been presented. A rational, but aggressive, treatment has been described. The morbidity of the procedure is minimal when proper instrumentation is available. The postoperative results are esthetically pleasing because, with radiation, there is so much fibrosis that facial contour is satisfactory even after a hemimandibulectomy.

Humans↗
PubMedDate not supplied

Mandible stabilization between ablative and reconstructive surgery.

The biphase external skeletal-fixation splint (Morris splint) for mandibular stabilization has been used in cases of ablative surgery. It is a practical approach to stabilization for patients whether or not they undergo reconstruction, either immediate or delayed. The Morris splint can be applied without increasing the time required for major resection. It can be left in place for prolonged periods, but it still allows easy surgical access and easy postoperative care and observation. While not a new tool, it has been little used by the head and neck cancer surgeon, probably because it has not been presented for this purpose but rather for treating fractures. A practical approach to the use of the Morris biphase splint is presented, as well as the indications for its use and some results of our experience with this tool.

Bone Screws↗
PubMedDate not supplied

Conformation of aminosuccinyl dipeptides Ac-L-X-L-Asu-NMe from empirical energy calculations.

The aminosuccinyl (Asu) residue is formed as intermediate in some peptide and protein reactions. Potential energy calculations, using the parameters of the empirical conformational energy program for peptides (ECEPP), were performed on blocked X-Asu dipeptides, where X = Gly, Ala, Ser, Val and Pro. Results indicate that intra-residue interactions are dominant, and the low-energy dipeptide conformations correspond to the low-energy single-residue minima. Comparisons were made with previous results from energy calculations on blocked Asu-X dipeptides (X = Gly, Ala, Ser and Val).

Dipeptides↗
PubMedDate not supplied

Deamidation via cyclic imide of asparaginyl peptides: dependence on salts, buffers and organic solvents.

The deamidation reaction of Asn side chain was studied in the presence of the chemicals usually used at high concentration in the purification and crystallization of peptides and proteins. All the experiments were performed on the model peptide Boc-L-Asn-Gly-Gly-NH2. The pathway of the reaction is not affected by the medium used; in all cases it proceeds through a succinimide intermediate giving a mixture of isoaspartyl and aspartyl peptide. However, the rate of the reaction significantly depends on the solvent: the addition of organic solvents to an aqueous solution of the peptide has the general effect of decreasing the reaction rate, which, on the other hand, is strongly enhanced by a high concentration of organic and inorganic buffers. Only a minor influence is exerted by aprotic salts and polyethylene glycol.

Amides↗
PubMedDate not supplied

Conformation of aminosuccinyl dipeptides Ac-Asu-X-NHMe from empirical energy calculations.

Conformational energy calculations were carried out on the N-acetyl-N'-methylamides of aminosuccinyl (Asu) peptides. Computations were performed using a procedure analogous to that of the ECEPP/2 program, on N-Ac-L-Asu-NMe, N-Ac-L-Asu-L-X-NHMe, where X = Gly, Ala, Ser, Val and N-Ac-D-Asu-L-Ala-NHMe. With the exception of N-Ac-L-Asu-L-Val-NHMe, the lowest-energy forms of all the dipeptides correspond to a beta-bend conformation of type II' or II for a L,L and D,L sequence, respectively. When X = Val, the folded conformation is destabilized, and more extended conformations are preferred. The puckering of the cyclic imide has a small but meaningful influence on the relative energies of the minima. The calculations were shown to be in agreement with available experimental data.

Dipeptides↗