Disentangling of incomplete fusion dynamics at low energies ≈ 4-6 MeV/A

371-375An experiment has been performed for the measurements of forward recoil range distributions (FRRDs) of evaporation residues (ERs) using 16O beam on the target 148Nd to explore the incomplete fusion (ICF) dynamics at low projectile energy ≈ 4-6 MeV/A. In the present work, FRRDs of ERs 159,158Er(xn), 160g,159Ho(pxn), 157,155Dy(αxn) and 155Tb(αpxn) have been measured. The measured FRRDs of ERs have been compared with their theoretical mean ranges, calculated using code SRIM. These present results obtained from FRRDs measurements show that full and partial linear momentum transfer components are involved. This indicates that the ERs populated through α-emission channels are not only produced via complete fusion, but also through incomplete fusion dynamics. The present analysis indicates that the incomplete fusion contribution increases with projectile energy. This increment in incomplete fusion contribution is due to the increase in breakup probability of projectile 16O into 12C + 4He/ α with projectile energy

Disentangling of incomplete fusion dynamics at low energies ≈ 4-6 MeV/A

An experiment has been performed for the measurements of forward recoil range distributions (FRRDs) of evaporation residues (ERs) using 16O beam on the target 148Nd to explore the incomplete fusion (ICF) dynamics at low projectile energy ≈ 4-6 MeV/A. In the present work, FRRDs of ERs 159,158Er(xn), 160g,159Ho(pxn), 157,155Dy(αxn) and 155Tb(αpxn) have been measured. The measured FRRDs of ERs have been compared with their theoretical mean ranges, calculated using code SRIM. These present results obtained from FRRDs measurements show that full and partial linear momentum transfer components are involved. This indicates that the ERs populated through α-emission channels are not only produced via complete fusion, but also through incomplete fusion dynamics. The present analysis indicates that the incomplete fusion contribution increases with projectile energy. This increment in incomplete fusion contribution is due to the increase in breakup probability of projectile 16O into 12C + 4He/ α with projectile energy

Effect of projectile breakup in the system 19F + 154Sm

An attempt was made to understand the role of various entrance channel parameters on incomplete fusion dynamics by the measurements of excitation functions of evaporation residues populated via complete and incomplete fusion dynamics in the system 19F + 154Sm at projectile energy ≈ 4-6 MeV/A. The stacked foil activation technique followed by offline gamma ray spectrometry was employed in these measurements. The measured excitation functions of various evaporation residues populated have been analyzed within the framework of statistical model code PACE-4. It has been observed that the measured excitation functions of xn and pxn emission channels agree well with the theoretical predictions of PACE-4. On the other hand, the measured excitation functions of α-emission channels have been found significantly enhanced over their theoretical predictions. This enhancement may be attributed to the incomplete fusion of the projectile 19F as the calculations for incomplete fusion are not included in statistical model calculations. The incomplete fusion fraction has been deduced from the present measurements. Further, a systematic study has also been performed, which shows that the incomplete fusion increases significantly with entrance channel mass asymmetry at low projectile energy, differently for different projectiles

Effect of projectile breakup in the system 19F + 154Sm

386-391An attempt was made to understand the role of various entrance channel parameters on incomplete fusion dynamics by the measurements of excitation functions of evaporation residues populated via complete and incomplete fusion dynamics in the system 19F + 154Sm at projectile energy ≈ 4-6 MeV/A. The stacked foil activation technique followed by offline gamma ray spectrometry was employed in these measurements. The measured excitation functions of various evaporation residues populated have been analyzed within the framework of statistical model code PACE-4. It has been observed that the measured excitation functions of xn and pxn emission channels agree well with the theoretical predictions of PACE-4. On the other hand, the measured excitation functions of α-emission channels have been found significantly enhanced over their theoretical predictions. This enhancement may be attributed to the incomplete fusion of the projectile 19F as the calculations for incomplete fusion are not included in statistical model calculations. The incomplete fusion fraction has been deduced from the present measurements. Further, a systematic study has also been performed, which shows that the incomplete fusion increases significantly with entrance channel mass asymmetry at low projectile energy, differently for different projectiles

Loss of Niemann-Pick C1 or C2 Protein Results in Similar Biochemical Changes Suggesting That These Proteins Function in a Common Lysosomal Pathway

Niemann-Pick Type C (NPC) disease is a lysosomal storage disorder characterized by accumulation of unesterified cholesterol and other lipids in the endolysosomal system. NPC disease results from a defect in either of two distinct cholesterol-binding proteins: a transmembrane protein, NPC1, and a small soluble protein, NPC2. NPC1 and NPC2 are thought to function closely in the export of lysosomal cholesterol with both proteins binding cholesterol in vitro but they may have unrelated lysosomal roles. To investigate this possibility, we compared biochemical consequences of the loss of either protein. Analyses of lysosome-enriched subcellular fractions from brain and liver revealed similar decreases in buoyant densities of lysosomes from NPC1 or NPC2 deficient mice compared to controls. The subcellular distribution of both proteins was similar and paralleled a lysosomal marker. In liver, absence of either NPC1 or NPC2 resulted in similar alterations in the carbohydrate processing of the lysosomal protease, tripeptidyl peptidase I. These results highlight biochemical alterations in the lysosomal system of the NPC-mutant mice that appear secondary to lipid storage. In addition, the similarity in biochemical phenotypes resulting from either NPC1 or NPC2 deficiency supports models in which the function of these two proteins within lysosomes are linked closely

Heterotrimeric G proteins and the single-transmembrane domain IGF-II/M6P receptor: functional interaction and relevance to cell signaling

The G protein-coupled receptor (GPCR) family represents the largest and most versatile group of cell surface receptors. Classical GPCR signaling constitutes ligand binding to a seven-transmembrane domain receptor, receptor interaction with a heterotrimeric G protein, and the subsequent activation or inhibition of downstream intracellular effectors to mediate a cellular response. However, recent reports on direct, receptor-independent G protein activation, G protein-independent signaling by GPCRs, and signaling of nonheptahelical receptors via trimeric G proteins have highlighted the intrinsic complexities of G protein signaling mechanisms. The insulin-like growth factor-II/mannose-6 phosphate (IGF-II/M6P) receptor is a single-transmembrane glycoprotein whose principal function is the intracellular transport of lysosomal enzymes. In addition, the receptor also mediates some biological effects in response to IGF-II binding in both neuronal and nonneuronal systems. Multidisciplinary efforts to elucidate the intracellular signaling pathways that underlie these effects have generated data to suggest that the IGF-II/M6P receptor might mediate transmembrane signaling via a G protein-coupled mechanism. The purpose of this review is to outline the characteristics of traditional and nontraditional GPCRs, to relate the IGF-II/M6P receptor’s structure with its role in G protein-coupled signaling and to summarize evidence gathered over the years regarding the putative signaling of the IGF-II/M6P receptor mediated by a G protein

Altered levels and distribution of IGF-II/M6P receptor and lysosomal enzymes in mutant APP and APP + PS1 transgenic mouse brains

The insulin-like growth factor-II/mannose-6-phosphate (IGF-II/M6P) receptor participates in the trafficking of lysosomal enzymes from the trans-Golgi network or the cell surface to lysosomes. In Alzheimer's disease (AD) brains, marked up-regulation of the lysosomal system in vulnerable neuronal populations has been correlated with altered metabolic functions. To establish whether IGF-II/M6P receptors and lysosomal enzymes are altered in the brain of transgenic mice harboring different familial AD mutations, we measured the levels and distribution of the receptor and lysosomal enzymes cathepsins B and D in select brain regions of transgenic mice overexpressing either mutant presenilin 1 (PS1; PS1M146L+L286V), amyloid precursor protein (APP; APPKM670/671NL+V717F) or APP + PS1 (APPKM670/671NL+V717F + PS1M146L+L286V) transgenes. Our results revealed that levels and expression of the IGF-II/M6P receptor and lysosomal enzymes are increased in the hippocampus and frontal cortex of APP and APP + PS1, but not in PS1, transgenic mouse brains compared with wild-type controls. The changes were more prominent in APP + PS1 than in APP single transgenic mice. Additionally, all β-amyloid-containing neuritic plaques in the hippocampal and cortical regions of APP and APP + PS1 transgenic mice were immunopositive for both lysosomal enzymes, whereas only a subset of the plaques displayed IGF-II/M6P receptor immunoreactivity. These results suggest that up-regulation of the IGF-II/M6P receptor and lysosomal enzymes in neurons located in vulnerable regions reflects an altered functioning of the endosomal–lysosomal system which may be associated with the increased intracellular and/or extracellular Aβ deposits observed in APP and APP + PS1 transgenic mouse brains

Heterotrimeric G proteins and the single-transmembrane domain IGF-II/M6P receptor : Functional interaction and relevance to cell signaling

The G protein-coupled receptor (GPCR) family represents the largest and most versatile group of cell surface receptors. Classical GPCR signaling constitutes ligand binding to a seven-transmembrane domain receptor, receptor interaction with a heterotrimeric G protein, and the subsequent activation or inhibition of downstream intracellular effectors to mediate a cellular response. However, recent reports on direct, receptor-independent G protein activation, G protein-independent signaling by GPCRs, and signaling of nonheptahelical receptors via trimeric G proteins have highlighted the intrinsic complexities of G protein signaling mechanisms. The insulin-like growth factor-II/mannose-6 phosphate (IGF-II/M6P) receptor is a single-transmembrane glycoprotein whose principal function is the intracellular transport of lysosomal enzymes. In addition, the receptor also mediates some biological effects in response to IGF-II binding in both neuronal and nonneuronal systems. Multidisciplinary efforts to elucidate the intracellular signaling pathways that underlie these effects have generated data to suggest that the IGF-II/M6P receptor might mediate transmembrane signaling via a G protein-coupled mechanism. The purpose of this review is to outline the characteristics of traditional and nontraditional GPCRs, to relate the IGF-II/M6P receptor's structure with its role in G protein-coupled signaling and to summarize evidence gathered over the years regarding the putative signaling of the IGF-II/M6P receptor mediated by a G protein

Validity of scaling property and iso-centrifugal approximation in quasielastic barrier distribution: the first experimental verification

For the first time, we have simultaneously measured fusion and quasielastic excitation functions for an intermediate mass system for angular momentum, $$\ell \sim 0$$ using a recoil mass spectrometer. We have extracted barrier distributions using three different sets of data recorded simultaneously for the reaction $$^{16}$$O+$$^{142}$$Ce: (a) fusion excitation function from measurement of evaporation residues at angle, $$\theta _{\text {lab}} = 0^{\circ }$$, (b) quasielastic excitation function at center of mass scattering angle, $$\theta _{\text {c.m.}} = \pi$$ via measurement of scattered target-like ions at $$\theta _{\text {lab}} = 0^{\circ }$$ and (c) quasielastic excitation functions from measurement of scattered projectile-like ions at two large angles. We show that the four barrier distributions yield nearly identical results with a single peak. However, the centroids of the barriers extracted from quasielastic data at large angles are lower by $$\sim 600$$ keV compared to the same of the barriers extracted from fusion and quasielastic data for $$\ell \sim 0$$. This is the first experimental verification of the validity of scaling property with respect to $$\ell$$ and iso-centrifugal approximation in extracting fusion barrier distribution from quasielastic scattering. This work also points to the importance of extracting barrier distribution from quasielastic measurements at $$\theta _{\mathrm {c.m.}} = \pi$$ for systems for which measuring fusion excitation function with high precision is not feasible