A topological similarity measure for proteins.

We introduce a new measure for assessing similarity among chemical structures, based on well-established computational-topology algorithms. We argue that although the method considers geometry, it is more than a mere geometric similarity measure, as it takes into account, on different geometric scales, the important topological features of the compared structures. We prove that our measure is rigorous and complies with the proper mathematical requirements. We validate the method through comparing different configurations of simple zinc finger proteins and present an application on ligands binding to membrane-proteINS extracted from the Directory of Useful Decoys: Enhanced database and corresponding decoys. This article is part of a Special Issue entitled: Viral membrane proteins - Channels for cellular networking.

Psychophysical characterization of auditory temporal and frequency streaming capacities for listeners with different levels of musical expertise.

Temporal and frequency auditory streaming capacities were assessed for non-musician (NM), expert musician (EM), and amateur musician (AM) listeners using a local-global task and an interleaved melody recognition task, respectively. Data replicate differences previously observed between NM and EM, and reveal that while AM exhibits a local-over-global processing change comparable to EM, their performance for segregating a melody embedded in a stream remains as poor as NM. The observed group partitioning along the temporal-frequency auditory streaming capacity map suggests a sequential, two-step development model of musical learning, whose contributing factors are discussed.

Multiple sclerosis iron rim lesions are linked to impaired cervical spinal cord integrity using the T1/T2-weighted ratio.

BACKGROUND AND PURPOSE: In multiple sclerosis (MS), iron rim lesions (IRLs) are characterized by pronounced tissue matrix damage. The T1/T2-weighted (T1/T2w) ratio represents a postprocessing MRI approach to investigate tissue integrity, but studies investigating spinal cord pathology are missing until now. The aim of this study was to characterize tissue integrity using the T1/T2w ratio in lesions and the normal-appearing white and gray matter (NAWM, NAGM) in the spinal cord and brain in MS patients with and without brain IRLs. METHODS: Forty MS patients (20 patients with at least one brain IRL and 20 age- and sex-matched patients without IRLs) were included. Normalized cross-sectional area (nCSA) of the upper cervical cord was calculated in addition to T1/T2w values and standard brain and spinal cord MRI parameters. RESULTS: Patients with IRLs had higher disability scores, a smaller nCSA, and a higher cervical T2 lesion volume. T1/T2w values of brain IRLs were significantly lower compared to non-IRLs (p < .001). Furthermore, T1/T2w values of lesions were significantly lower compared to the NAGM and NAWM, both in the brain and the spinal cord (p < .05 for all comparisons). T1/T2w values of the NAGM and NAWM in the brain and spinal cord did not statistically differ between the IRL group and the non-IRL group. CONCLUSION: IRLs constitute an imaging marker of disease severity. T1/T2w ratio maps represent an interesting technique to capture diffuse tissue properties. Calculation of T1/T2w ratio maps of the spinal cord might provide additional insights into the pathophysiological processes of MS.

MRI predictors for the conversion from contrast-enhancing to iron rim multiple sclerosis lesions.

BACKGROUND: In multiple sclerosis (MS), iron rim lesions (IRLs) are characterized by progressive tissue matrix damage. Therefore, early identification could represent an interesting target for therapeutic intervention to minimize evolving tissue damage. The aim of this study was to identify magnetic resonance imaging (MRI) parameters predicting the conversion from contrast-enhancing to IRLs. METHODS: We retrospective identified MS patients scanned on the same 3 T MRI system presenting at least one supratentorial contrast-enhancing lesion (CEL) and a second MRI including susceptibility-weighted images after at least 3 months. On baseline MRI, pattern of contrast-enhancement was categorized as "nodular" or "ring-like", apparent diffusion coefficient (ADC) maps were assessed for the presence of a peripheral hypointense rim. Lesion localization, quantitative volumes (ADC, lesion volume) and the presence of a central vein were assessed. RESULTS: Eighty-nine acute contrast-enhancing lesions in 54 MS patients were included. On follow-up, 16/89 (18%) initially CELs converted into IRLs. CELs that converted into IRLs were larger and demonstrated significantly more often a ring-like contrast-enhancement pattern and a peripheral hypointense rim on ADC maps. Logistic regression model including the covariables pattern of contrast-enhancement and presence of a hypointense rim on ADC maps showed the best predictive performance (area under the curve = 0.932). DISCUSSION: The combination of a ring-like contrast-enhancement pattern and a peripheral hypointense rim on ADC maps has the ability to predict the evolution from acute to IRLs. This could be of prognostic value and become a target for early therapeutic intervention to minimize the associated tissue damage.

Carrier systems for bone morphogenetic proteins: An overview of biomaterials used for dentoalveolar and maxillofacial bone regeneration.

Different types of biomaterials have been used to fabricate carriers to deliver bone morphogenetic proteins (BMPs) in both dentoalveolar and maxillofacial bone regeneration procedures. Despite that absorbable collagen sponge (ACS) is considered the gold standard for BMP delivery, there is still some concerns regarding its use mainly due to its poor mechanical properties. To overcome this, novel systems are being developed, however, due to the wide variety of biomaterial combination, the heterogeneous assessment of newly formed tissue, and the intended clinical applications, there is still no consensus regarding which is more efficient in a particular clinical scenario. The combination of two or more biomaterials in different topological configurations has allowed specific controlled-release patterns for BMPs, improving their biological and mechanical properties compared with classical single-material carriers. However, more basic research is needed. Since the BMPs can be used in multiple clinical scenarios having different biological and mechanical needs, novel carriers should be developed in a context-specific manner. Thus, the purpose of this review is to gather current knowledge about biomaterials used to fabricate delivery systems for BMPs in both dentoalveolar and maxillofacial contexts. Aspects related with the biological, physical and mechanical characteristics of each biomaterial are also presented and discussed.