High-Pressure Mechanistic Insight into Bioinorganic NO Chemistry

Pressure is one of the most important parameters controlling the kinetics of chemical reactions. The ability to combine high-pressure techniques with time-resolved spectroscopy has provided a powerful tool in the study of reaction mechanisms. This review is focused on the supporting role of high-pressure kinetic and spectroscopic methods in the exploration of nitric oxide bioinorganic chemistry. Nitric oxide and other reactive nitrogen species (RNS) are important biological mediators involved in both physiological and pathological processes. Understanding molecular mechanisms of their interactions with redox-active metal/non-metal centers in biological targets, such as cofactors, prosthetic groups, and proteins, is crucial for the improved therapy of various diseases. The present review is an attempt to demonstrate how the application of high-pressure kinetic and spectroscopic methods can add additional information, thus enabling the mechanistic interpretation of various NO bioinorganic reactions.

Surface-enhanced resonance Raman spectroscopy of heme proteins on a gold grid electrode

The combination of surface-enhanced resonance Raman spectroscopy (SERRS) and electrochemistry is an ideal tool to study the redox process of the heme proteins and is often performed on silver electrodes. In this manuscript, we present an approach using a microstructured gold surface that serves as the electrochemical working electrode, and at the same time, acts as SERS active substrate. The cell requires a micromolar concentration of sample at the electrode surface. Even if the performance of the gold grid as SERS substrate exhibited a smaller enhancement factor than expected for silver, oxidized and reduced spectra of proteins (Сyt c, Hb and Mb) monolayers could be obtained and the characteristic redox dependent shifts of the marker bands ν₁₉, ν₄ and ν₁₀ were seen. The easy modification protocol and the higher stability of the gold electrode towards oxidative currents are the advantages of the present spectroeletrochemical cell. Finally, FDTD simulations confirm that the roughness of the gold grid has an effect on the Raman enhancement of the adsorbed proteins.

Rapid phenotyping towards personalized malaria medicine

Malaria is major public health concerns which continues to claim the lives of more than 435,000 people each year. The challenges with anti-malarial drug resistance and detection of low parasitaemia forms an immediate barrier to achieve the fast-approaching United Nations Sustainable Development Goals of ending malaria epidemics by 2030. In this Opinion article, focusing on the recent published technologies, in particularly the nuclear magnetic resonance (NMR)-based diagnostic technologies, the authors offer their perspectives and highlight ways to bring these point-of-care technologies towards personalized medicine. To this end, they advocate an open sourcing initiative to rapidly close the gap between technological innovations and field implementation.

Quantitative imaging of intraerythrocytic hemozoin by transient absorption microscopy

Hemozoin, the heme detoxification end product in malaria parasites during their growth in the red blood cells (RBCs), serves as an important marker for diagnosis and treatment target of malaria disease. However, the current method for hemozoin-targeted drug screening mainly relies on in vitro β-hematin inhibition assays, which may lead to false-positive events due to under-representation of the real hemozoin crystal. Quantitative in situ imaging of hemozoin is highly desired for high-throughput screening of antimalarial drugs and for elucidating the mechanisms of antimalarial drugs. We present transient absorption (TA) imaging as a high-speed single-cell analysis platform with chemical selectivity to hemozoin. We first demonstrated that TA microscopy is able to identify β-hematin, the artificial form of hemozoin, from the RBCs. We further utilized time-resolved TA imaging to in situ discern hemozoin from malaria-infected RBCs with optimized imaging conditions. Finally, we quantitatively analyzed the hemozoin amount in RBCs at different infection stages by single-shot TA imaging. These results highlight the potential of TA imaging for efficient antimalarial drug screening and drug mechanism investigation.

Portable Device for Optical Quantification of Hemozoin in Diluted Blood Samples

OBJECTIVE

This paper focuses on a novel and portable device prototype with optical detectors to quickly and efficiently detect hemozoin (Hz) in blood, aiming at malaria diagnostics.

METHODS

Taking advantage of the particular features of malaria parasite in infected blood, particularly the Hz formation, the main innovation described is a portable device for the optical quantification of parasitic Hz in blood, through optical absorbance spectrophotometry. This device comprises detection chambers for fluidic samples, an optical emission and detection system, and a power supply system to provide autonomy. The working principle is based on colorimetric detection, by absorbance, at six specific wavelengths. A detection algorithm relates the absorbance values at all wavelengths to quantify the Hz concentration, thus working as a biomarker of malaria presence and stage.

RESULTS

Under the tested conditions, e.g., in fluidic samples containing synthetic Hz, hemoglobin, and diluted whole blood, the device detected Hz above 1 μg/mL concentrations with 100% sensitivity and 96.3% specificity.

CONCLUSION

This paper features an autonomous, portable, 1-min analysis time, and low-cost per test device, without the need for samples, centrifugation, allowing the use of whole blood.

SIGNIFICANCE

The presented device is a step ahead for meeting the growing clinical demands for reliable, rapid, portable, and quantitative malaria diagnosis.

Lipids, hemoproteins and carotenoids in alive Rhodotorula mucilaginosa cells under pesticide decomposition - Raman imaging study

Various species of yeasts are gaining attention as producers of nutraceuticals and biofuels and due to their capacity to biodegrade chemical waste. Rhodotorula mucilaginosa is one of the most oleaginous species of yeast, an efficient de novo carotenoid producer and was reported to be capable of decomposing of organic pesticides. In this work we studied the influence of a toxic pesticide, diazinone, on production of storage (lipids) and protective (carotenoids, hemoproteins) compounds by Rh. mucilaginosa alive cells with the help of Raman imaging. It occurred that the yeast in non-oleaginous phase and aerobic environment was rich in carotenoids and their level increased significantly under incubation with diazinone, while anaerobic environment resulted in production of both carotenoids and hemoproteins and the level of the latter decreased under the influence of the pesticide. For yeasts in oleaginous phase, it was concluded that lipid production (via triggering of NAD⁺ accumulation and increase of the NO level) resulted in nitrosative stress leading to flavohemoprotein synthesis and was associated with the increase of the mitochondrial activity.

Hemozoin detection may provide an inexpensive, sensitive, 1-minute malaria test that could revolutionize malaria screening

Malaria remains widespread throughout the tropics and is a burden to the estimated 3.5 billion people who are exposed annually. The lack of a fast and accurate diagnostic method contributes to preventable malaria deaths and its continued transmission. In many areas diagnosis is made solely based on clinical presentation. Current methods for malaria diagnosis take more than 20 minutes from the time blood is drawn and are frequently inaccurate. The introduction of an accurate malaria diagnostic that can provide a result in less than 1 minute would allow for widespread screening and treatment of endemic populations, and enable regions that have gained a foothold against malaria to prevent its return. Using malaria parasites' waste product, hemozoin, as a biomarker for the presence of malaria could be the tool needed to develop this rapid test.

[Hemozoin detection in malaria diagnosis]

In malaria parasites, hemozion is often called malaria pigment. Plasmodium spp. digest hemoglobin and release high quantity of free heme, which is a non-protein component of hemoglobin. Until recent years, researchers have found that hemozoin has many effects on malaria parasites. This paper reviews the hemozoin detection apllied in malaria diagnosis.

Haemozoin detection in infected erythrocytes for Plasmodium falciparum malaria diagnosis-prospects and limitations

Several methods based on the detection of the parasite-specific pigment haemozoin (Hz) in blood are currently being investigated as alternative diagnostic methods for malaria. Although this approach may appear attractive, the fact that in Plasmodium falciparum (P. f.) malaria, the severity of which should give it the highest diagnostic priority, the fact that most circulating intra-erythrocytic P. f. parasites contain little or no Hz raises some concern. We used flow cytometry to investigate the possibilities and limitations of the detection of intra-erythrocytic Hz in malaria infected patient blood samples and in vitro cultures. However, reliable detection of ring-forms or young trophozoites of P. f. parasites could not be achieved, although one-quarter of mature parasites could be detected after 24-48 h in culture. Our results strongly suggest that, although it may be useful for monitoring maturation, detection of intra-erythrocytic Hz by flow cytometry will not provide an optimal method for diagnosis of P. falciparum malaria.

Magnetic field enriched surface enhanced resonance Raman spectroscopy for early malaria diagnosis

Hemozoin is a by-product of malaria infection in erythrocytes, which has been explored as a biomarker for early malaria diagnosis. We report magnetic field-enriched surface-enhanced resonance Raman spectroscopy (SERRS) of β-hematin crystals, which are the equivalent of hemozoin biocrystals in spectroscopic features, by using magnetic nanoparticles with iron oxide core and silver shell (Fe(3)O(4)@Ag). The external magnetic field enriches β-hematin crystals and enhances the binding between β-hematin crystals and magnetic nanoparticles, which provides further improvement in SERRS signals. The magnetic field-enriched SERRS signal of β-hematin crystals shows approximately five orders of magnitude enhancement in the resonance Raman signal, in comparison to about three orders of magnitude improvement in the SERRS signal without the influence of magnetic field. The improvement has led to a β-hematin detection limit at a concentration of 5 nM (roughly equivalent to 30 parasites/μl at the early stages of malaria infection), which demonstrates the potential of magnetic field-enriched SERRS technique in early malaria diagnosis.

Relation between falciparum malaria and bacteraemia in Kenyan children: a population-based, case-control study and a longitudinal study

BACKGROUND

Many investigators have suggested that malaria infection predisposes individuals to bacteraemia. We tested this hypothesis with mendelian randomisation studies of children with the malaria-protective phenotype of sickle-cell trait (HbAS).

METHODS

This study was done in a defined area around Kilifi District Hospital, Kilifi, Kenya. We did a matched case-control study to identify risk factors for invasive bacterial disease, in which cases were children aged 3 months to 13 years who were admitted to hospital with bacteraemia between Sept 16, 1999, and July 31, 2002. We aimed to match two controls, by age, sex, location, and time of recruitment, for every case. We then did a longitudinal case-control study to assess the relation between HbAS and invasive bacterial disease as malaria incidence decreased. Cases were children aged 0-13 years who were admitted to hospital with bacteraemia between Jan 1, 1999, and Dec 31, 2007. Controls were born in the study area between Jan 1, 2006, and June 23, 2009. Finally, we modelled the annual incidence of bacteraemia against the community prevalence of malaria during 9 years with Poisson regression.

RESULTS

In the matched case-control study, we recruited 292 cases-we recruited two controls for 236, and one for the remaining 56. Sickle-cell disease, HIV, leucocyte haemozoin pigment, and undernutrition were positively associated with bacteraemia and HbAS was strongly negatively associated with bacteraemia (odds ratio 0·36; 95% CI 0·20-0·65). In the longitudinal case-control study, we assessed data from 1454 cases and 10,749 controls. During the study period, the incidence of admission to hospital with malaria per 1000 child-years decreased from 28·5 to 3·45, with a reduction in protection afforded by HbAS against bacteraemia occurring in parallel (p=0·0008). The incidence of hospital admissions for bacteraemia per 1000 child-years also decreased from 2·59 to 1·45. The bacteraemia incidence rate ratio associated with malaria parasitaemia was 6·69 (95% CI 1·31-34·3) and, at a community parasite prevalence of 29% in 1999, 62% (8·2-91) of bacteraemia cases were attributable to malaria.

INTERPRETATION

Malaria infection strongly predisposes individuals to bacteraemia and can account for more than half of all cases of bacteraemia in malaria-endemic areas. Interventions to control malaria will have a major additional benefit by reducing the burden of invasive bacterial disease.

FUNDING

Wellcome Trust.

Detection of malarial byproduct hemozoin utilizing its unique scattering properties

The scattering characteristics of the malaria byproduct hemozoin, including its scattering distribution and depolarization, are modeled using Discrete Dipole Approximation (DDA) and compared to those of healthy red blood cells. Scattering (or dark-field) spectroscopy and imaging are used to identify hemozoin in fresh rodent blood samples. A new detection method is proposed and demonstrated using dark-field in conjunction with cross-polarization imaging and spectroscopy. SNRs greater than 50:1 are achieved for hemozoin in fresh blood without the addition of stains or reagents. The potential of such a detection system is discussed.

Hematological predictors of increased severe anemia in Kenyan children coinfected with Plasmodium falciparum and HIV-1

Malaria and HIV-1 are coendemic in many developing countries, with anemia being the most common pediatric hematological manifestation of each disease. Anemia is also one of the primary causes of mortality in children monoinfected with either malaria or HIV-1. Although our previous results showed HIV-1(+) children with acute Plasmodium falciparum malaria [Pf(+)] have more profound anemia, potential causes of severe anemia in coinfected children remain unknown. As such, children with P. falciparum malaria (aged 3-36 months, n = 542) from a holoendemic malaria transmission area of western Kenya were stratified into three groups: HIV-1 negative [HIV-1(-)/Pf(+)]; HIV-1 exposed [HIV-1(exp)/Pf(+)]; and HIV-1 infected [HIV-1(+)/Pf(+)]. Comprehensive clinical, parasitological, and hematological measures were determined upon enrollment. Univariate, correlational, and hierarchical regression analyses were used to determine differences among the groups and to define predictors of worsening anemia. HIV-1(+)/Pf(+) children had significantly more malarial pigment-containing neutrophils (PCN), monocytosis, increased severe anemia (Hb < 6.0 g/dL), and nearly 10-fold greater mortality within 3 months of enrollment. Common causes of anemia in malaria-infected children, such as increased parasitemia or reduced erythropoiesis, did not account for worsening anemia in the HIV-1(+)/Pf(+) group nor did carriage of sickle cell trait or G6PD deficiency. Hierarchical multiple regression analysis revealed that more profound anemia was associated with elevated PCM, younger age, and increasing HIV-1 status ([HIV-1(-) --> HIV-1(exp) --> HIV-1(+)]. Thus, malaria/HIV-1 coinfection is characterized by more profound anemia and increased mortality, with acquisition of monocytic pigment having the most detrimental impact on Hb levels.

The haem-accessibility in leghaemoglobin of Lupinus luteus as observed by proton magnetic relaxation

Using the solvent-protons' longitudinal magnetic relaxation rates (p.m.r.) for Lupinus luteus leghaemoglobin derivatives the accessibility of the haem has been evaluated by our "stereo-chemical p.m.r. titration" method with nonexchangeable protons of aliphatic lower alcohols in otherwise deuterated solutions. The haem in leghaemoglobin is more accessible and its protein environment more flexible compared with vertebrate haemoglobins. The correlation time in aquometleghaemglobin aqueous solution has been determined by measuring the frequency dispersion of the p.m.r. rates between 6.1 and 93 MHZ. Taking into account the measured value of tauc = (7.7 +/- 0.5 x 10(-10) s the iron-to-proton inter-spin distances have been calculated. The significance of these distances as well as the electronic g-factor anisotrophy for elucidation of fine structural details of the haem-environment are discussed.

Plasmodium berghei: parasite clearance after treatment with dihydroartemisinin in an asplenic murine malaria model

Clinical reports indicate that malaria-infected asplenic patients have a reduced capacity for parasite clearance despite intensive antimalarial therapy. The aim of this study was to evaluate the efficacy of dihydroartemisinin in an asplenic murine malaria model. Mice were inoculated with Plasmodium berghei parasitised erythrocytes and received a single dose of dihydroartemisinin 56 h later, at 2-5% parasitaemia. Haematology, liver biochemistry and histopathology of key organs were performed to evaluate organ response to malaria infection. The nadir parasitaemia occurred 20 h after dihydroartemisinin administration, falling 2.8- to 6.0-fold and 2.7- to 6.9-fold in asplenic and intact mice, respectively, (10-100 mg/kg). Histopathology indicated increased stimulation of liver function/activity during malaria infection of asplenic mice (as compared to intact mice). Overall efficacy of single-dose dihydroartemisinin treatment in asplenic mice was similar to intact mice although the rate of recrudescence in asplenic mice was significantly greater than intact mice at 30 and 100 mg/kg. The asplenic murine malaria model could be used in pre-clinical studies of splenic function and clearance of malaria parasites, pathophysiological studies or antimalarial drug efficacy in asplenia.

Raman acoustic levitation spectroscopy of red blood cells and Plasmodium falciparum trophozoites

Methods to probe the molecular structure of living cells are of paramount importance in understanding drug interactions and environmental influences in these complex dynamical systems. The coupling of an acoustic levitation device with a micro-Raman spectrometer provides a direct molecular probe of cellular chemistry in a containerless environment minimizing signal attenuation and eliminating the affects of adhesion to walls and interfaces. We show that the Raman acoustic levitation spectroscopic (RALS) approach can be used to monitor the heme dynamics of a levitated 5 microL suspension of red blood cells and to detect hemozoin in malaria infected cells. The spectra obtained have an excellent signal-to-noise ratio and demonstrate for the first time the utility of the technique as a diagnostic and monitoring tool for minute sample volumes of living animal cells.

In Situ Localization and Structural Analysis of the Malaria Pigment Hemozoin

Raman microspectroscopy was applied for an in situ localization of the malaria pigment hemozoin in Plasmodium falciparum-infected erythrocytes. The Raman spectra (lambdaexc=633 nm) of hemozoin show very intense signals with a very good signal-to-noise ratio. These in situ Raman signals of hemozoin were compared to Raman spectra of extracted hemozoin, of the synthetic analogue beta-hematin, and of hematin and hemin. beta-Hematin was synthesized according to the acid-catalyzed dehydration of hematin and the anhydrous dehydrohalogenation of hemin which lead to good crystals with lengths of about 5-30 microm. The Raman spectra (lambdaexc=1064 nm) of hemozoin and beta-hematin show almost identical behaviors, while some low wavenumber modes might be used to distinguish between the morphology of differently synthesized beta-hematin samples. The intensity pattern of the resonance Raman spectra (lambdaexc=568 nm) of hemozoin and beta-hematin differ significantly from those of hematin and hemin. The most striking difference is an additional band at 1655 cm(-1) which was only observed in the spectra of hemozoin and beta-hematin and cannot be seen in the spectra of hematin and hemin. Raman spectra of the beta-hematin dimer were calculated ab initio (DFT) for the first time and used for an assignment of the experimentally derived Raman bands. The calculated atomic displacements provide valuable insight into the most important molecular vibrations of the hemozoin dimer. With help from these DFT calculations, it was possible to assign the Raman band at 1655 cm(-1) to a mode located at the propionic acid side chain, which links the hemozoin dimers to each other. The Raman band at 1568 cm(-1), which has been shown to be influenced by an attachment of the antimalarial drug chloroquine in an earlier study, could be assigned to a C=C stretching mode spread across one of the porphyrin rings and is therefore expected to be influenced by a pi-pi-stacking to the drug.

Heme crystallization in the midgut of triatomine insects

Hemozoin (Hz) is a heme crystal produced by several blood-feeding organisms in order to detoxify free heme released upon hemoglobin (Hb) digestion. Here we show that heme crystallization also occurs in three species of triatomine insects. Ultraviolet-visible and infrared light absorption spectra of insoluble pigments isolated from the midgut of three triatomine species Triatoma infestans, Dipetalogaster maximus and Panstrongylus megistus indicated that all produce Hz. Morphological analysis of T. infestans and D. maximus midguts revealed the close association of Hz crystals to perimicrovillar membranes and also as multicrystalline assemblies, forming nearly spherical structures. Heme crystallization was promoted by isolated perimicrovillar membranes from all three species of triatomine bugs in vitro in heat-sensitive reactions. In conclusion, the data presented here indicate that Hz formation is an ancestral adaptation of Triatominae to a blood-sucking habit and that the presence of perimicrovillar membranes plays a central role in this process.

[Method of determination of the content of hemoglobin-like proteins in heterogenic mixtures]

A spectrophotometric method of quantification of hemoglobin-like proteins, which makes it possible to determine their concentration in mixtures of various composition, was proposed. This method is based on comparing the optical density of different redox forms of proteins when their spectra are superposed at the isosbestic point. The coefficients used in calculations were determined by us. The proposed technique is simple and does not require special procedures. It was tested using myoglobin solutions of various concentrations, myoglobin solutions containing other proteins, and solutions of leghemoglobin (a myoglobin-like protein from legumes).

[Electrophoretic patterns of salivary hemeproteins (nitrophorines) of Rhodnius colombiensis and R. prolixus (Hemiptera, Reduviidae, Triatominae)]

INTRODUCTION

Salivary hemeprotein electrophoresis in starch gels is a recent technique used for differentiation of Rhodnius species with great phenotypic similarity. Furthermore, populations of the same species can be differentiated from geographically separated locales. Of the 15 described Rhodnius species in Latin America, at least eight have been reported in Colombia.

OBJECTIVE

To use the salivary hemeproteins electrophoresis for R. prolixus and R. colombiensis identification. These two species are phenotypically similar and have overlapping domestic and sylvatic cycles where they occur in the upper basin of the Magdalena river, Central Colombia.

MATERIAL AND METHODS

The content of salivary glands of each insect was subjected to starch gel electrophoresis using glycine buffer, and the bands were revealed with 3,3',5,5'-tetramethylbenzidine. Band patterns were photographically recorded.

RESULTS

Electrophoretic patterns of salivary hemeproteins of R. prolixus and R. colombiensis were able to unequivocally differentiate the two species.

CONCLUSION

The usefulness of the starch gel technique for distinguishing between R. prolixus and R. colombiensis was demonstrated as an additional tool to the morphometric and molecular methods already in use for differentiation of these two species.

Two ligand-binding sites in the O2-sensing signal transducer HemAT: implications for ligand recognition/discrimination and signaling

We have identified a ligand (CO) accommodation cavity in the signal transducer sensor protein HemAT (heme-based aerotactic transducer) that allows us to gain single-molecule insights into the mechanism of gas sensor proteins. Specific mutations that are distal and proximal to the heme were designed to perturb the electrostatic field near the ligand that is bound to the heme and near the accommodated ligand in the cavity. We report the detection of a second site in heme proteins in which the exogenous ligand is accommodated in an internal cavity. The conformational gate that directs the ligand-migration pathway from the distal to the proximal site of the heme, where the ligand is trapped, has been identified. The data provide evidence that the heme pocket is the specific ligand trap and suggest that the regulatory mechanism may be tackled starting from more than one position in the protein. Based on the results, we propose a dynamic coupling between the two distinct binding sites as the underlying allosteric mechanism for gas recognition/discrimination that triggers a conformational switch for signaling by the oxygen sensor protein HemAT.

Spinning Disk Confocal Microscopy of Live, Intraerythrocytic Malarial Parasites. 1. Quantification of Hemozoin Development for Drug Sensitive versus Resistant Malaria

We have customized a Nipkow spinning disk confocal microscope (SDCM) to acquire three-dimensional (3D) versus time data for live, intraerythrocytic malarial parasites. Since live parasites wiggle within red blood cells, conventional laser scanning confocal microscopy produces blurred 3D images after reconstruction of z stack data. In contrast, since SDCM data sets at high x, y, and z resolution can be acquired in hundreds of milliseconds, key aspects of live parasite cellular biochemistry can be much better resolved on physiologically meaningful times scales. In this paper, we present the first 3D DIC transmittance "z stack" images of live malarial parasites and use those to quantify hemozoin (Hz) produced within the living parasite digestive vacuole, under physiologic conditions. Using live synchronized cultures and voxel analysis of sharpened DIC z stacks, we present the first quantitative in vivo analysis of the rate of Hz growth for chloroquine sensitive (CQS) versus resistant (CQR) malarial parasites. We present data for laboratory strains, as well as pfcrt transfectants expressing a CQR conferring mutant pfcrt gene. We also analyze the rate of Hz growth in the presence and absence of physiologically relevant doses of chloroquine (CQ) and verapamil (VPL) and thereby present the first in vivo quantification of key predictions from the well-known Fitch hypothesis for CQ pharmacology. In the following paper [Gligorijevic, B., et al. (2006) Biochemistry 45, pp 12411-12423], we acquire fluorescent images of live parasite DV via SDCM and use those to quantify DV volume for CQS versus CQR parasites.

Haemozoin (β-haematin) biomineralization occurs by self-assembly near the lipid/water interface

Several blood-feeding organisms, including the malaria parasite detoxify haem released from host haemoglobin by conversion to the insoluble crystalline ferriprotoporphyrin IX dimer known as haemozoin. To date the mechanism of haemozoin formation has remained unknown, although lipids or proteins have been suggested to catalyse its formation. We have found that beta-haematin (synthetic haemozoin) forms rapidly under physiologically realistic conditions near octanol/water, pentanol/water and lipid/water interfaces. Molecular dynamics simulations show that a precursor of the haemozoin dimer forms spontaneously in the absence of the competing hydrogen bonds of water, demonstrating that this substance probably self-assembles near a lipid/water interface in vivo.

Identification of an intermolecular disulfide bond in barley hemoglobin

Barley class-1 hemoglobin (Hb) and its mutated version (Cys(79) replaced by Ser) were overexpressed in Escherichia coli and purified to near homogeneity. Nano-electrospray ionization mass spectrometry (nano-ESI MS) showed that the mutated barley Hb was more readily dissociated to a monomer and was more susceptible to denaturation than the native form. The mutated Hb was oxidized to the ferric state approximately 10(3) times faster than the non-mutated form. The increased oxidation of the mutated Hb was a result of substitution of the cysteine with a serine and not a consequence of monomer formation, per se. Tandem mass spectrometry (MS/MS) analysis revealed that Cys(79) participated in intermolecular S-S bond formation. The rates of nitric oxide scavenging by non-mutated and mutated Hb were similar. We conclude that the cysteine residue is an important contributor to the quaternary and tertiary structure of barley hemoglobin. It however has no direct effect on nitric oxide-scavenging activity of barley Hb.

High prevalence of placental malaria and low birth weight in Sahelian periurban area

The impact of placental malaria in African urban areas is poorly documented. We therefore conducted a study during the rainy season in Dakar, an area with low malaria transmission. Two groups of delivering women were enrolled according to the detection of PfHRP2 in placental blood. Ten percent of the women were positive for parasites in the placenta, and microscopic examination showed, respectively, 17%, 22%, and 44% of past, acute, and chronic infection. The mean birth weight decreased drastically with the infection of the placenta (2,684 +/- 67 versus 3,085 +/- 66 g for controls), particularly with chronic infection. Chronic infection was not linked with parasiteamia in maternal venous blood. Seventy-six percent of positive women were anemic (46% of the controls). Severe anemia was also associated with chronic infection. Long-lasting infections are the most deleterious to mother and infant and are most likely associated with drug resistance of parasites.

Towards Combined Electrochemistry and Surface-Enhanced Resonance Raman of Heme Proteins: Improvement of Diffusion Electrochemistry of Cytochrome c at Silver Electrodes Chemically Modified with 4-Mercaptopyridine

To date, a successful combination of surface-enhanced resonance Raman spectroscopy (SERRS) and electrochemistry to study heme proteins is inhibited by the problems raised by the prerequisite to use silver as electrode metal. This paper indicates an approach to overcome these problems. It describes a quick and reproducible procedure to prepare silver electrodes chemically modified with 4-mercaptopyridine suitable to perform diffusion electrochemistry of cytochrome c (cyt c). The method involves the employment of a mechanical and a chemical treatment and avoids the use of alumina slurries and any electrochemical pretreatment. Cyclic voltammetry (CV) was used to test the electrochemical response of cyt c, and the CV signals were found identical with those obtained on gold electrodes under the same experimental conditions. Compared to previous literature, a significant improvement of the CV signal of cyt c at silver electrodes was achieved. Preliminary results show that this treatment can be also successfully employed for the preparation of SERRS-active electrodes.

Bioavailable iron and heme metabolism in Plasmodium falciparum

Iron metabolism is essential for cell function and potentially toxic because iron can catalyze oxygen radical production. Malaria-attributable anemia and iron deficiency anemia coincide as being treatable diseases in the developing world. In absolute amounts, more than 95% of Plasmodium metal biochemistry occurs in the acidic digestive vacuole where heme released from hemoglobin catabolism forms heme crystals. The antimalarial quinolines interfere with crystallization. Despite the completion of the Plasmodium genome, many 'gene gaps' exist in components of the metal pathways described in mammalian or yeast cells. Present evidence suggests that parasite bioavailable iron originates from a labile erythrocyte cytosolic pool rather than from abundant heme iron. Indeed the parasite has to make its own heme within two separate organelles, the mitochondrion and the apicomplast. Paradoxically, despite the abundance of iron within the erythrocyte, iron chelators are cytocidal to the Plasmodium parasite. Hemozoin has become a sensitive biomarker for laser desorption mass spectrometry detection of Plasmodium infection in both mice and humans.

Biochemical Survey on Episodic Localized Darkening in Turkey Deboned Thigh Meat Packaged in Modified Atmosphere

The color of food, especially meat and meat products, is a parameter that strongly influences consumer choice. In Italy, repeated cases of darkening in deboned thigh meat of male turkeys packaged in modified atmosphere (MAP; 80% 02, 20% CO2) have been reported. The pH, lipid oxidation (TBARS), heme proteins, and iron content were investigated in MAP samples of turkey males, females, and in oxygen-permeable film-packaged males. Furthermore, the absorbance spectrum (400 to 700 nm) of the meat extracts was analyzed to better delineate the evolution and characteristics of the darkening process. Results showed that darkening occurred only in males with higher content of total iron, independently of the content of heme proteins, which differs only between males and females. Furthermore, pH was higher in muscles taken as controls, with respect to muscles involved in the darkening, as well as in females. Finally, TBARS values were found to be higher in darkened regions than in not darkened ones, as well as in MAP samples with respect to oxygen-permeable film-packaged samples. These findings suggest that darkening occurrence might depend on kind of muscle, sex, and individual characteristics of the animals raised under the same breeding conditions.

Bullous Allergic Hypersensitivity to Bed Bug Bites Mediated by IgE against Salivary Nitrophorin

In Central Europe, bites from the common bed bug (Cimex lectularius) are nowadays rather uncommon. Nevertheless, infestations are sometimes observed in old framehouses and by immigration due to international travel and migration. The clinical picture of bug bites substantially varies between individuals, depending upon previous exposure and the degree of an immune response. The host immune response and potential protein antigens present in the saliva of C. lectularius or specific antibodies have not been characterized thus far. We describe a patient with bullous bite reactions after sequential contact with C. lectularius over a period of 1 year. In skin tests, we observed immediate reactions to the salivary gland solution of C. lectularius, which were followed by a pronounced partially blistering late-phase response. Immunoblot analysis of the patient's serum with salivary gland extracts and recombinant C. lectularius saliva proteins revealed specific IgE antibodies against the 32 kDa C. lectularius nitrophorin, but not to 37 kDa C. lectularius apyrase. Our data demonstrate that bullous cimicosis may be the late-phase response of an allergic IgE-mediated hypersensitivity to C. lectularius nitrophorin.

Molecular identification of adrenal inner zone antigen as a heme-binding protein

The adrenal inner zone antigen (IZA), which reacts specifically with a monoclonal antibody raised against the fasciculata and reticularis zones of the rat adrenal, was previously found to be identical with a protein variously named 25-Dx and membrane-associated progesterone receptor. IZA was purified as a glutathione S-transferase-fused or His(6)-fused protein, and its molecular properties were studied. The UV-visible absorption and EPR spectra of the purified protein showed that IZA bound a heme chromophore in high-spin type. Analysis of the heme indicated that it is of the b type. Site-directed mutagenesis studies were performed to identify the amino-acid residues that bind the heme to the protein. The results suggest that two Tyr residues, Tyr107 and Tyr113, and a peptide stretch, D99-K102, were important for anchoring the heme into a hydrophobic pocket. The effect of IZA on the steroid 21-hydroxylation reaction was investigated in COS-7 cell expression systems. The results suggest that the coexistence of IZA with CYP21 enhances 21-hydroxylase activity.

Assembly of layer-by-layer films of heme proteins and single-walled carbon nanotubes: electrochemistry and electrocatalysis

After being treated by mixed acids, single-walled carbon nanotubes (SWNTs) were shortened and had negatively charged groups on the surface. Positively charged hemoglobin or myoglobin at pH 5.0 was successfully assembled with SWNTs into layer-by-layer films on solid surfaces, designated as {SWNT/protein}n. While only those proteins in the first few bilayers closest to the electrode surface exhibited electroactivity, the {SWNT/protein}n films demonstrated a much higher fraction of electroactive proteins and better controllability in film construction compared with cast films of the proteins and carbon nanotubes. The proteins in the {SWNT/protein}n films retained their near-native structure at medium pH. The stable protein film electrode showed good electrocatalytic properties toward reduction of oxygen and hydrogen peroxide, demonstrating the potential application of the {SWNT/protein}n films as a new type of biosensor based on the direct electrochemistry of proteins without using mediators.

Biochemical characterization and vaccine potential of a heme-binding glutathione transferase from the adult hookworm Ancylostoma caninum

We report the cloning and expression of Ac-GST-1, a novel glutathione S-transferase from the adult hookworm Ancylostoma caninum, and its possible role in parasite blood feeding and as a vaccine target. The predicted Ac-GST-1 open reading frame contains 207 amino acids (mass, 24 kDa) and exhibited up to 65% amino acid identity with other nematode GSTs. mRNA encoding Ac-GST-1 was detected in adults, eggs, and larval stages, but the protein was detected only in adult hookworm somatic extracts and excretory/secretory products. Using antiserum to the recombinant protein, Ac-GST-1 was immunolocalized to the parasite hypodermis and muscle tissue and weakly to the intestine. Recombinant Ac-GST-1 was enzymatically active, as determined by conjugation of glutathione to a model substrate, and exhibited a novel high-affinity binding site for hematin. The possible role of Ac-GST-1 in parasite heme detoxification during hemoglobin digestion or heme uptake prompted interest in evaluating it as a potential vaccine antigen. Vaccination of dogs with Ac-GST-1 resulted in a 39.4% reduction in the mean worm burden and 32.3% reduction in egg counts compared to control dogs following larval challenge, although the reductions were not statistically significant. However, hamsters vaccinated with Ac-GST-1 exhibited statistically significant worm reduction (53.7%) following challenge with heterologous Necator americanus larvae. These studies suggest that Ac-GST-1 is a possible drug and vaccine target for hookworm infection.

On-line chemiluminescence detection for isoelectric focusing of heme proteins on microchips

In this paper we present a sensitive chemiluminescence (CL) detection of heme proteins coupled with microchip IEF. The detection principle was based on the catalytic effects of the heme proteins on the CL reaction of luminol-H2O2 enhanced by para-iodophenol. The glass microchip and poly(dimethylsiloxane) (PDMS)/glass microchip for IEF were fabricated using micromachining technology in the laboratory. The modes of CL detection were investigated and two microchips (glass, PDMS/glass) were compared. Certain proteins, such as cytochrome c, myoglobin, and horseradish peroxidase, were focused by use of Pharmalyte pH 3-10 as ampholytes. Hydroxypropylmethylcellulose was added to the sample solution in order to easily reduce protein interactions with the channel wall as well as the EOF. The focused proteins were transported by salt mobilization to the CL detection window. Cytochrome c, myoglobin, and horseradish peroxidase were well separated within 10 min on a glass chip and the detection limits (S/N=3) were 1.2x10(-7), 1.6x10(-7), and 1.0x10(-10) M, respectively.

Assessment of a simplified method for counting leukocytic malaria pigment

Severe and fatal malaria is associated with the increased presence of malaria hemozoin in peripheral phagocytes. Large studies of this relationship are hampered by the fact that identifying and counting phagocytes on thick blood smears is time consuming. Distinguishing which mononuclear cells are monocytes and which granulocytes are neutrophils requires time and careful training. In this study, we evaluated a simplified method in which only the proportions of hemozoin-containing mononuclear cells and granulocytes are counted. Thick blood films from 471 Gabonese children with malaria were evaluated. We found a linear relationship and a strong correlation between the proportions of hemozoin-containing monocytes versus mononuclear cells (r = 0.85) and neutrophils versus polymorphonuclear cells (r = 0.93), respectively. The two methods had similar predictive values, as estimated by receiver operating characteristics curves. This simplified method can be used to estimate the amount of extra-erythrocytic pigment in peripheral blood, and we suggest that it may be particularly suitable for very large studies.

Performance evaluation of automated depolarization analysis for detecting clinically unsuspected malaria in endemic countries

This prospective study evaluated the efficiency of automated depolarization analysis for recognition of unsuspected malaria by haemozoin detection during routine full blood count (FBC) screening of 676 randomly selected out-patients in a malaria hypoendemic area of Senegal. An additional 123 patients with clinically suspected malaria were studied for comparison. Of the 799 samples, 648 (81.1%) were categorized as malaria-negative, 83 (10.4%) as malaria-positive, and 68 as treated (early convalescence) or subclinical malaria (indirect evidence of infection). At a discrimination level of one or more atypical pigment-containing monocytes (PCM), negative and positive agreement was found to be 95.6% and 91.6% respectively for all malaria-negative and parasite-positive samples combined. Increasing the discriminator to two or more PCM events improved the overall agreement to 97.5%. Multivariate analysis showed that the only significant risk factor for the presence of PCM (odds ratio>200) was malaria infection. In the randomly selected group of 676 patients, 41 unsuspected cases of malaria infection were detected using the panel of reference diagnostic tests, and 37 (90.2%) of these had atypical PCM. The detection of clinically unrecognized malaria infection as part of a routine FBC procedure is a potentially useful extended application for laboratories in countries with endemic malaria.

β-Hematin (Hemozoin) Mediated Decompostion of Polyunsaturated Fatty Acids to 4-Hydroxy-2-nonenal

beta-Hematin is an important heme metabolite of malarial infection. Its role as an agent mediating the formation of the reactive electrophile 4-hydroxynonenal (HNE) from polyunsaturated fatty acids was investigated. In vitro formation of HNE was found to be facilitated by the presence of hemozoin in a concentration-dependent fashion. The reactivity of HNE derived from reaction with beta-hematin was confirmed through its ability to form protein adducts on myoglobin.

Electrostatic Adsorption of Heme Proteins Alternated with Polyamidoamine Dendrimers for Layer-by-layer Assembly of Electroactive Films

A novel thin film of heme proteins, including hemoglobin (Hb), myoglobin (Mb), and catalase (Cat), was successfully assembled layer by layer with polyamidoamine (PAMAM) dendrimers on different solid surfaces. At pH 7.0, protonated PAMAM possesses positive surface charges, whereas the proteins have net negative surface charges at pH above their isoelectric points. Thus, layer-by-layer {PAMAM/protein}(n)() films were assembled with alternate adsorption of oppositely charged PAMAM and proteins from their aqueous solutions mainly by electrostatic interaction. The assembly process was monitored by quartz crystal microbalance (QCM), UV-vis spectroscopy, and cyclic voltammetry (CV). The growth of the protein multilayer films was regular and linear, whereas the electroactivity of the films was only extended to a few bilayers. CVs of {PAMAM/protein}(n)() films showed a pair of well-defined and nearly reversible peaks characteristic of the protein heme Fe(III)/Fe(II) redox couples. Although {PAMAM/Hb}(n)() and {PAMAM/Mb}(n)() films showed very similar properties, {PAMAM/Cat}(n)() films displayed different and unique characters. The substrates with biological or environmental significance, such as oxygen, hydrogen peroxide, trichloroacetic acid, and nitrite, were catalytically reduced at {PAMAM/protein}(n)() film electrodes, showing the potential applicability of the films as new types of biosensors or bioreactors based on direct electrochemistry of the proteins. Both the electrochemical and electrocatalytic activity of {PAMAM/protein}(n)() films can be tailored precisely by controlling the number of bilayers or the film thickness.

Heat-Resistant Oxygen-Carrying Hemoproteins Consist of Recombinant Xylanases and Synthetic Iron(II) Porphyrin

Synthetic iron(II) porphyrin (FeP) is equivalently incorporated into recombinant Thermotoga maritima xylanase B (TMX; family F/10 of glycoside hydrolase), producing a heat-resistant artificial hemoprotein (TMX-FeP) that can bind and release oxygen (O(2)) in aqueous medium (pH 7.3, 25 degrees C) in the same manner as hemoglobin and myoglobin. The oxygenated species was sufficiently stable; the half-lifetime against the ferric state (tau(1/2)) was 5 h. This O(2)-carrying hemoprotein showed a high degree of thermal stability over a wide range of temperatures up to 90 degrees C (tau(1/2) = 5 min at 90 degrees C and 9 min at 75 degrees C). Dictyoglomus thermophilum xylanase B (DTX; family G/11) also incorporates FeP, and DTX-FeP showed identical O(2)-binding parameters and thermostability. TMX-FeP is capable of catalyzing the beta-1,4-d-xylan hydrolysis reaction. Its larger K(m) value compared to that of TMX itself suggested competitive FeP binding to the active site of the host enzyme.

Identification of heme binding protein complexes in murine erythroleukemic cells: Study by a novel two-dimensional native separation - liquid chromatography and electrophoresis

In the current postgenomic era there is a growing interest in analysis of protein complexes in their native state. Here we present a novel two-dimensional separation technique for assessment of native protein complexes. The method combines native chromatography with native electrophoresis. The approach was used to study heme-binding protein complexes in murine erythroleukemia cells. The cells were metabolically labeled with [(59)Fe]-heme and cellular lysates were separated by anion-exchange chromatography. Fractions containing the (59)Fe isotope were collected, concentrated and further separated by native gel electrophoresis. A total of 13 radioactive protein bands were detected and analyzed by liquid chromatography-tandem mass spectrometry. Thirty-three individual proteins were identified and attributed to four novel multiprotein complexes representing four different 'snapshots' of cellular events involved in hemoglobin biosynthesis.

A sensitive method for the detection of proteins by high-efficiency fluorescence quenching

A successful method for the detection of electron transfer proteins such as cytochrome c, hemoglobin and myoglobin has been developed based on the fluorescence quenching of semiconductor nanocrystals. High sensitivity and a good linear relationship are obtained.

Pseudoeosinophilia associated with malaria infection determined in the Sysmex XE-2100 hematology analyzer

Hemozoin is known to be an end product of hemoglobin digestion by the malaria parasite. Hemozoin is a birefringent crystal, and thus hemozoin-containing white blood cells (WBCs) may show the atypical light scattering pattern. The purpose of this study was to investigate pseudoeosinophilia associated with malaria infection using a Sysmex XE-2100 hematology analyzer (Sysmex Corporation, Kobe, Japan). The study group included 16 patients with malaria infection. Of these, 38% showed erroneously high eosinophil counts and atypical eosinophil distributions in the WBCs scattergram, which was due to the presence of hemozoin-containing neutrophils. In two patients, their erroneously high eosinophil counts declined as the parasitemia decreased with treatment. In conclusion, hematologists should consider the possibility of pseudoeosinophilia as a result of hemozoin-containing WBCs and confirm the WBC differential count by microscopy in cases of malaria infection.

Rapid detection of malaria infection in vivo by laser desorption mass spectrometry

Rapid diagnosis leading to effective treatment is essential to control escalating infectious diseases such as malaria. Malaria pigment (hemozoin) detection by laser desorption mass spectometry (LDMS) was recently shown to be a sensitive (<10 parasites/muL) technique for detecting Plasmodium falciparum parasites cultured in human blood. To examine the use of LDMS in a rapid new malaria screening assay, we followed the time course of P. yoelii infections in mice in parallel with light microscopy and a colorimetric hemozoin assay. Hemozoin was detected by LDMS in 0.3 muL of blood within two days of infection independently of the inoculating dose of 10(6), 10(4), or 10(2) parasite-infected erythrocytes. Microscopy and colorimetric hemozoin determinations lagged the LDMS detection of infections by 2-4 and 3-5 days, respectively, except at the highest inoculation dose. The LDMS detection of hemozoin is a potentially more rapid screen than light microscopy for detecting malaria infection in this mouse model at parasitemias <0.1%.

Direct electrochemistry and electrocatalysis of heme-proteins entrapped in agarose hydrogel films

Three heme-proteins, including myoglobin (Mb), hemoglobin (Hb) and horseradish peroxidase (HRP), were immobilized on edge-plane pyrolytic graphite (EPG) electrodes by agarose hydrogel. The proteins entrapped in the agarose film undergo fast direct electron transfer reactions, corresponding to FeIII = e- --> FeII. The formal potential (E degrees'), the apparent coverage (Gamma), the electron transfer coefficient (alpha) and the apparent electron transfer rate constant (ks) were calculated by integrating cyclic voltammograms or performing nonlinear regression analysis of square wave voltammetric (SWV) experimental data. The E degrees's are linearly dependent on solution pH (redox Bohr effect), indicating that the electron transfer was proton-coupled. Ultraviolet visible (UV-Vis) and reflection-absorption infrared (RAIR) spectra suggest that the conformation of proteins in the agarose film are little different from that proteins alone, and the conformation changes reversibly in the range of pH 3.0-10.0. Atomic force microscopy (AFM) images of the agarose film indicate a stable and crystal-like structure formed possibly due to the synergistic interaction of hydrogen bonding between N,N-dimethylformamide (DMF), agarose hydrogel and heme-proteins. This suggests a strong interaction between the heme-proteins and the agarose hydrogel. DMF plays an important role in immobilizing proteins and enhancing electron transfer between proteins and electrodes. The mechanisms for catalytic reduction of hydrogen peroxide and nitric oxide (NO) by proteins entrapped in agarose hydrogel were also explored.

Recent developments in the 13 C NMR spectroscopic analysis of paramagnetic hemes and heme proteins

Despite the wealth of information that has been obtained from the study of paramagnetic hemes and heme proteins by 1H NMR spectroscopy, there are certain limitations imposed by the nature of paramagnetically affected resonances that are difficult to overcome. Although it has long been recognized that 13C NMR spectroscopy is likely to be a powerful complementary technique to overcome some of these limitations, the low sensitivity and low natural abundance of 13C nuclei has resulted in a lag in the application of 13C NMR spectroscopy to the study of paramagnetic hemes and heme proteins. The tremendous advances in methodology and instrumentation witnessed in the NMR field, coupled to the advent of recombinant DNA methods that have made possible the preparation and purification of significant quantities of proteins, and the biosynthesis of 13C-labeled heme, have contributed to an increased interest in the study of paramagnetic heme active sites by 13C NMR spectroscopy. As a consequence, 13C NMR spectroscopy is emerging as a powerful tool to study heme electronic structure and structure-function relationships in heme-containing proteins. In this report we strive to summarize some of the recent developments in the analysis of paramagnetic hemes and heme-containing proteins by 13C NMR spectroscopy.

Spectrophotometric determination of de novo hemozoin/β-hematin formation in an in vitro assay

Formation of hemozoin in the malaria parasite, due to its unique nature, is an attractive molecular target. Several laboratories have been trying to unravel the molecular mechanism of hemozoin biosynthesis within the parasite digestive vacuoles. Use of different assay protocols for in vitro beta-hematin (synthetic identical to hemozoin) formation by these laboratories has led to inconsistent and often contradictory findings. Much of the difficulty may be attributed to oligomeric heme aggregates, which may be indistinguishable in some detection approaches if adequate separation of beta-hemtin is not achieved. Therefore, there is an urgent need for a widely accepted protocol for in vitro beta-hematin formation. We describe here a spectrophotometric assay for in vitro beta-hematin formation. The assay has been validated with the Plasmodium falciparum lysate, the parasite lipid extracts, and some commercially available fatty acids, which are known to initiate/catalyze beta-hematin formation in vitro. The necessity for multiple wash steps for accurate quantification of de novo hemozoin/beta-hematin formation was verified experimentally. It was necessary to wash the pellet, which contains beta-hematin and heme aggregates, sequentially with Tris/SDS buffer and alkaline bicarbonate solution for complete removal of monomeric heme and heme aggregates and accurate quantification of beta-hematin formed during the assay. The pellets and side products in the supernatant were characterized by infrared spectroscopy. No beta-hematin formation occurred in the absence of a catalytic/initiating factor. Based on these findings, a filtration-based assay that uses 96-well microplates, and which has important application in in vitro screening and identification of novel inhibitors of hemozoin formation as potential blood schizontocidal antimalarials, has been developed.

Cytoglobin/STAP, its unique localization in splanchnic fibroblast-like cells and function in organ fibrogenesis

Cytoglobin/stellate cell activation-associated protein (Cygb/STAP) consists of a new class of hexacoordinate globin superfamily, which was recently discovered by a proteome analysis on the rat hepatic stellate cells. Unlike haemoglobin, myoglobin, and neuroglobin, Cygb/STAP is ubiquitously expressed in several organs, although its detailed localization has not been clarified. Immunohistochemistry and immunoelectron microscopy revealed that Cygb/STAP is uniquely localized in fibroblast-like cells in splanchnic organs, namely the vitamin A-storing cell lineage, but neither in epithelial cells, endothelial cells, muscle cells, blood cells, macrophages, nor dermal fibroblasts. The expression of Cygb/STAP was upregulated in fibrotic lesions of the pancreas and kidney in which activated fibroblast-like cells or myofibroblasts are known to increase in number. In cultured hepatic stellate cells, Cygb/STAP expression was augmented by the stimulation with sera, platelet-derived growth factor-BB, and transforming growth factor-beta 1. Overexpression of Cygb/STAP in NIH 3T3 cells induced the cells to lessen migratory activities and increase the expression of collagen alpha1(I) mRNA. These results indicate that Cygb/STAP is a tissue globin uniquely localized in splanchnic fibroblastic cell lineage and may play a role in fibrotic organ disorder.

Raman imaging of hemozoin within the food vacuole ofPlasmodium falciparumtrophozoites

Micro-Raman spectra of hemozoin encapsulated within the food vacuole of a Plasmodium falciparum-infected erythrocyte are presented. The spectrum of hemozoin is identical to the spectrum of beta-hematin at all applied excitation wavelengths. The unexpected observation of dramatic band enhancement of A(1g) modes including nu(4) (1374 cm(-1)) observed when applying 780 nm excitation enabled Raman imaging of hemozoin in the food vacuole. This unusual enhancement, resulting from excitonic coupling between linked porphyrin moieties in the extended porphyrin array, enables the investigation of hemozoin within its natural environment for the first time.