Gas-Phase Synthesis for Label-Free Biosensors: Zinc-Oxide Nanowires Functionalized with Gold Nanoparticles.

Metal oxide semiconductor nanowires have important applications in label-free biosensing due to their ease of fabrication and ultralow detection limits. Typically, chemical functionalization of the oxide surface is necessary for specific biological analyte detection. We instead demonstrate the use of gas-phase synthesis of gold nanoparticles (Au NPs) to decorate zinc oxide nanowire (ZnO NW) devices for biosensing applications. Uniform ZnO NW devices were fabricated using a vapor-solid-liquid method in a chemical vapor deposition (CVD) furnace. Magnetron-sputtering of a Au target combined with a quadrupole mass filter for cluster size selection was used to deposit Au NPs on the ZnO NWs. Without additional functionalization, we electrically detect DNA binding on the nanowire at sub-nanomolar concentrations and visualize individual DNA strands using atomic force microscopy (AFM). By attaching a DNA aptamer for streptavidin to the biosensor, we detect both streptavidin and the complementary DNA strand at sub-nanomolar concentrations. Au NP decoration also enables sub-nanomolar DNA detection in passivated ZnO NWs that are resilient to dissolution in aqueous solutions. This novel method of biosensor functionalization can be applied to many semiconductor materials for highly sensitive and label-free detection of a wide range of biomolecules.

A chiroselective peptide replicator.

The origin of homochirality in living systems is often attributed to the generation of enantiomeric differences in a pool of chiral prebiotic molecules, but none of the possible physiochemical processes considered can produce the significant imbalance required if homochiral biopolymers are to result from simple coupling of suitable precursor molecules. This implies a central role either for additional processes that can selectively amplify an initially minute enantiomeric difference in the starting material, or for a nonenzymatic process by which biopolymers undergo chiroselective molecular replication. Given that molecular self-replication and the capacity for selection are necessary conditions for the emergence of life, chiroselective replication of biopolymers seems a particularly attractive process for explaining homochirality in nature. Here we report that a 32-residue peptide replicator, designed according to our earlier principles, is capable of efficiently amplifying homochiral products from a racemic mixture of peptide fragments through a chiroselective autocatalytic cycle. The chiroselective amplification process discriminates between structures possessing even single stereochemical mutations within otherwise homochiral sequences. Moreover, the system exhibits a dynamic stereochemical 'editing' function; in contrast to the previously observed error correction, it makes use of heterochiral sequences that arise through uncatalysed background reactions to catalyse the production of the homochiral product. These results support the idea that self-replicating polypeptides could have played a key role in the origin of homochirality on Earth.

Segregation of a pure form of spastic paraplegia and NOR insertion into Xq11.2.

A 3-year-old boy, his 7-year-old brother, and a maternal uncle had a pure form of spastic paraplegia and a variant X chromosome with a faintly stained gap at Xq11.2. The mother of the propositus also had the variant X chromosome but was clinically unaffected. Three other unaffected females in the family did not have the variant X chromosome. The gaps in the variant X chromosome from the affected members and the mother were Ag-NOR staining positive, C-banding negative, rDNA FISH analysis positive, and alpha-satellite FISH analysis negative. The gap, therefore, represented an insertion of the nucleolus organizer region (NOR) derived from the short arm of an acrocentric chromosome. The variant X chromosome of the mother was randomly inactivated, as evidenced by BrdU replication analysis of her Epstein-Barr virus-transformed lymphoblastoid cells. Because mutations of the proteolipid protein gene at Xq21 have been responsible for a pure form of spastic paraplegia, this was also investigated but found to be negative in all affected relatives. Summing up these findings, it is proposed that the NOR insertion in the affected members of the family disrupted a hitherto unknown gene for a pure form of spastic paraplegia, situated at Xq11.2, and caused the disorder.

Emergence of symbiosis in peptide self-replication through a hypercyclic network.

Symbiosis is an association between different organisms that leads to a reciprocal enhancement of their ability to survive. Similar mutually beneficial relationships can operate at the molecular level in the form of a hypercycle, a collective of two or more self-replicating species interlinked through a cyclic catalytic network. The superposition of cross-catalysis onto autocatalytic replication integrates the members of the hypercycle into a single system that reproduces through a second-order (or higher) form of nonlinear autocatalysis. The hypercycle population as a whole is therefore able to compete more efficiently for existing resources than any one member on its own. In addition, the effects of beneficial mutations of any one member are spread over the entire population. The formation of hypercycles has been suggested as an important step in the transition from inanimate to living chemistry, and a large number of hypercycles are expected to be embedded within the complex networks of living systems. But only one naturally occurring hypercycle has been well documented, while two autocatalytic chemical systems may contain vestiges of hypercyclic organization. Here we report a chemical system that constitutes a clear example of a minimal hypercyclic network, in which two otherwise competitive self-replicating peptides symbiotically catalyse each others' production.

Central carcinoma of the jaw. A survey of 28 cases in the Japanese literature.

A survey of the Japanese literature revealed 28 well-documented cases of central carcinoma of the jaws. There was no sex predominance and the mandible was the site of involvement in 26 cases. The most common initial symptom was local swelling, which was followed in order of frequency by spontaneous pain, paraesthesia of the lower lip, discomfort, loosening of teeth and trismus. On clinical examination, local swelling which was often accompanied by variable symptoms was an almost constant finding. Radiographic appearance varied from unilocular to worm-eaten type radiolucencies which were often surrounded by indistinct margins on close examination. Radical surgery, combined with irradiation and/or chemotherapy was the principal treatment in most cases, but there were 4 cases in which the lesions were simply excised under a tentative diagnosis of cyst; local recurrence was noted in 5 cases. Regional lymph node metastasis and lung metastasis were observed in 8 and 2 cases, respectively. No definite conclusion was drawn with regard to the prognosis because of the short follow-up period. Histologically, epidermoid carcinoma was most frequently seen, but odontogenic cyst was confirmed to be the site of origin in 3 cases only.

Reimplantation of frozen-thawed autogenous mandible after resection of an ameloblastoma.

A case of immediate reimplantation of a frozen-thawed autogenous mandible with a mixture of iliac bone, marrow, and particulate hydroxylapatite in a 12-year-old boy with an ameloblastoma of the mandible is described and the conditions leading to successful outcome of the procedure are discussed.

Marsupialization as a possible diagnostic aid in cystic ameloblastoma. Case report.

Two cases of cystic ameloblastoma are described in which the diagnosis was established after marsupialization. Although the clinical and radiographic findings strongly suggested the diagnosis of ameloblastoma, the initial incisional biopsy specimens consisted of cystic walls lined with squamous epithelium which showed in both cases no evidence of ameloblastic proliferation. Marsupialization could be a diagnostic aid in these cases since relief of intracystic pressure may trigger regeneration of a solid mass of tumour in a monocystic ameloblastoma with cells possessing potentiality for spontaneous proliferation.

Non-Hodgkin's lymphoma of the gingiva. A case report.

An unusual case of non-Hodgkin's lymphoma with a progressive, necrotizing ulcer of the gingiva is reported. An establishment od diagnosis was difficult because of lack of malignancy in repeated biopsy specimens. Radiotherapy combined with administration of anti-tumor agents was effective in producing a rapid remission of the oral lesion, but multiple metastases appeared in the skin and the patient died 7 months after the onset of the initial symptoms. The tumor was regarded as being of gingival origin because of the absence of a primary focus in any other site of the body.