Fluorescence Intensity and Intermittency as Tools for Following Dopamine Bioconjugate Processing in Living Cells

CdSe/ZnS quantum dots (QDs) conjugated to biomolecules that quench their fluorescence, particularly dopamine, have particular spectral properties that allow determination of the number of conjugates per particle, namely, photoenhancement and photobleaching. In this work, we quantify these properties on a single-particle and ensemble basis in order to evaluate their usefulness as a tool for indicating QD uptake, breakdown, and processing in living cells. This creates a general framework for the use of fluorescence quenching and intermittency to better understand nanoparticle-cell interactions

FACTORS AFFECTING MIGRATION FROM THE CROATIAN RURAL AREA

U radu se daju rezultati istraživanja migracija u seoskom području Republike Hrvatske. Cilj je istražiti čimbenike koji utječu na iseljavanje seoskog stanovništva Republike Hrvatske. Istraživanje je provedeno 2007. godine na uzorku od 914 ispitanika dobi od 24 do 45 godina u seoskom području Republike Hrvatske. Odabir naselja i ispitanika bio je slučajan. Provedeno istraživanje pokazuje da su najveće poteškoće života u hrvatskom seoskom području gospodarske naravi, manjak zaposlenja, slaba mogućnost izbora zanimanja i niža zarada u odnosu na zaposlenje u gradu. Petina ispitanika nije zadovoljna uvjetima seoskog života i namjerava se iseliti. To je zabrinjavajući pokazatelj budući da se radi o populaciji koja je u pravilu završila proces obrazovanja i većinom osnovala obitelj. Najviše mogućih iseljenika, što je bilo i za očekivati, je iz gospodarski nerazvijenih područja Republike Hrvatske. Daljnja depopulacija hrvatskog sela bila bi pogubna, a njene najveće posljedice bile bi: prevelika urbanizacija, posebice velikih gradova, daljnji neravnomjerni razvitak Republike Hrvatske te nedovoljno iskorištenje prostornog, proizvodnog i ljudskog potencijala. S obzirom na strateški cilj ulaska Republike Hrvatske u Europsku uniju, navedeno predstavlja bitno ograničenje njene uspješne prilagodbe europskoj ekonomskoj integraciji. Iseljavanje seoskog pučanstva može se spriječiti prvenstveno povećanjem zaposlenosti i dohotka te stvaranjem takve fizičke i društvene infrastrukture u seoskom području koja će bitno poboljšati životne uvjete seoskog pučanstva. Seoska područja, poglavito gospodarski nerazvijena, nemaju dovoljno vlastitih mogućnosti za ubrzanje razvoja odnosno za nužno smanjivanje razlika u kakvoći življenja prema gradskim područjima. Zbog toga je nužno da njihov razvojni proces više nego dosada potpomogne Država osmišljenim mjerama regionalnog razvoja, uz svekoliku potporu lokalne uprave i samouprave. U tome bi svoj znatan obol trebalo dati novo-osnovano Ministarstvo za regionalni razvoj.The paper presents results of the research study on migrations in rural areas of the Republic of Croatia. The aim was to determine factors influencing migrations of rural population in Croatia. The research was carried out in 2007 on 914 respondents from 25 to 45 years of age. The rural communities and respondents were selected on a random basis. The study results indicate that the major difficulties in rural life in Croatia are of economic nature: lack of employment opportunities, inadequate choice of profession and lower income in comparison with employment in urban areas. One fifth of the respondents is not satisfied with conditions of rural life and intends to leave villages. This is a very disturbing indicator, since it refers to population, which in general, has finished education and started a family. As we expect, the largest number of potential migrants comes from economically underdeveloped Croatian areas. Further depopulation of Croatian villages would have dramatic effects, and the worst consequences would be excessive urbanization, especially of large cities, further uneven development of the Republic of Croatia, and insufficient utilization of spatial, production and human resources. Since the strategic Croatian goal is to become a member of the European Union, this is a major obstacle to its successful adjustment to the European economic integration. The migration of rural population could be prevented primarily by increase in employment and income opportunities and creation of such physical and social infrastructure in rural areas that would considerably improve living conditions for rural population. The rural areas, particularly underdeveloped, have no adequate capacities for intensification of its development and diminishing differences in their quality of life compared to urban areas. Thus, the state support is increasingly required by introducing measures of regional development with complementary support of the local government. The newly founded Ministry of Regional Development is therefore inevitable in this process

Effects of pH, cations and lipids on the structure, stability and function of bacteriorhodopsin

Ph.D.Mostafa A. El-Saye

Proton Transfer Reactions in Native and Deionized Bacteriorhodopsin upon Delipidation and Monomerization

We have investigated the role of the native lipids on bacteriorhodopsin (bR) proton transfer and their connection with the cation-binding role. We observe that both the efficiency of M formation and the kinetics of M rise and decay depend on the lipids and lattice but, as the lipids are removed, the cation binding is a much less important factor for the proton pumping function. Upon 75% delipidation using 3-[(cholamidopropyl)dimethylammonio]-propanesulfonate (CHAPS), the M formation and decay kinetics are much slower than the native, and the efficiency of M formation is ∼30%–40% that of the native. Upon monomerization of bR by Trition X-100, the efficiency of M recovers close to that of the native (depending on pH), M formation is ∼10 times faster, and M decay kinetics are comparable to native at pH 7. The same results on the M intermediate are observed if deionized blue bR (deI bbR) is treated with these detergents (with or without pH buffers present), even though deionized blue bR containing all the lipids has no photocycle. This suggests that the cation(s) has a role in native bR that is different than in delipidated or monomerized bR, even so far as to suggest that the cation(s) becomes unimportant to the function as the lipids are removed

Probing synaptic signaling with quantum dots

Synapses are the principal substrates of neuronal communication in the brain. Neuroscientists are trying to understand how the remodeling of synapses at the molecular level leads to changes in learning and memory. The lateral movement of neurotransmitter receptors is emerging as an important mechanism in the control of synaptic transmission. However, our understanding of the spatial dynamics of membrane receptors at synapses has been limited largely because of a lack of appropriate tools to resolve single receptors in living cells. Fluorescent quantum dots represent promising probes to monitor individual synaptic receptors in living neural circuits. Bats and colleagues (Bats, Groc, and Choquet, Neuron 53, 719, 2007) used quantum dots to track the ins and outs of glutamate receptors at synapses, showing that the receptors bring company as they diffuse in the synapse to become trapped via their partner’s local connections. Their study sheds new light on the mechanisms used by synapses to change their efficacy, which may impact on our understanding of the cellular and molecular basis of learning and memory

Comparison of the dynamics of the primary events of bacteriorhodopsin in its trimeric and monomeric states.

In this paper, femtosecond pump-probe spectroscopy in the visible region of the spectrum has been used to examine the ultrafast dynamics of the retinal excited state in both the native trimeric state and the monomeric state of bacteriorhodopsin (bR). It is found that the excited state lifetime (probed at 490 nm) increases only slightly upon the monomerization of bR. No significant kinetic difference is observed in the recovery process of the bR ground state probed at 570 nm nor in the fluorescent state observed at 850 nm. However, an increase in the relative amplitude of the slow component of bR excited state decay is observed in the monomer, which is due to the increase in the concentration of the 13-cis retinal isomer in the ground state of the light-adapted bR monomer. Our data indicate that when the protein packing around the retinal is changed upon bR monomerization, there is only a subtle change in the retinal potential surface, which is dependent on the charge distribution and the dipoles within the retinal-binding cavity. In addition, our results show that 40% of the excited state bR molecules return to the ground state on three different time scales: one-half-picosecond component during the relaxation of the excited state and the formation of the J intermediate, a 3-ps component as the J changes to the K intermediate where retinal photoisomerization occurs, and a subnanosecond component during the photocycle