Resolving structure and mechanical properties at the nanoscale of viruses with frequency modulation atomic force microscopy.
ABSTRACT Structural Biology (SB) techniques are particularly successful in solving virus structures. Taking advantage of the symmetries, a heavy averaging on the data of a large number of specimens, results in an accurate determination of the structure of the sample. However, these techniques do not provide true single molecule information of viruses in physiological conditions. To answer many fundamental questions about the quickly expanding physical virology it is important to develop techniques with the capability to reach nanometer scale resolution on both structure and physical properties of individual molecules in physiological conditions. Atomic force microscopy (AFM) fulfills these requirements providing images of individual virus particles under physiological conditions, along with the characterization of a variety of properties including local adhesion and elasticity. Using conventional AFM modes is easy to obtain molecular resolved images on flat samples, such as the purple membrane, or large viruses as the Giant Mimivirus. On the contrary, small virus particles (25-50 nm) cannot be easily imaged. In this work we present Frequency Modulation atomic force microscopy (FM-AFM) working in physiological conditions as an accurate and powerful technique to study virus particles. Our interpretation of the so called "dissipation channel" in terms of mechanical properties allows us to provide maps where the local stiffness of the virus particles are resolved with nanometer resolution. FM-AFM can be considered as a non invasive technique since, as we demonstrate in our experiments, we are able to sense forces down to 20 pN. The methodology reported here is of general interest since it can be applied to a large number of biological samples. In particular, the importance of mechanical interactions is a hot topic in different aspects of biotechnology ranging from protein folding to stem cells differentiation where conventional AFM modes are already being used.
Article: Enterovirus inactivation in soil.[show abstract] [hide abstract]
ABSTRACT: The inactivation of radioactively labeled poliovirus type 1 and coxsackievirus B 1 in soils saturated with surface water, groundwater, and septic tank liquor was directly proportional to temperature. Virus persistence was also related to soil type and the liquid amendment in which viruses were suspended. At 37 degrees C, no infectivity was recovered from saturated soil after 12 days; at 4 degrees C, viruses persisted for at least 180 days. No infectivity was recovered from dried soil regardless of temperature, soil type, or liquid amendment. Additional experiments showed that evaporation of soil water was largely responsible for the decreased recovery of infectivity from drying soil. Increased rates of virus inactivation at low soil moisture levels were also demonstrated.Applied and Environmental Microbiology 11/1979; 38(4):694-701. · 3.83 Impact Factor
[show abstract] [hide abstract]
ABSTRACT: Uterine fibroids are the most common pelvic tumors in women and are a significant cause of morbidity for women of reproductive age. Today, there are a variety of less invasive alternatives available to hysterectomy, such as myomectomy, hormonal therapy, uterine artery embolization, and more recently magnetic resonance-guided focused ultrasound surgery (MRgFUS). With this technique, ultrasound waves are focused through intact skin of the anterior abdominal wall resulting in localized thermal tissue ablation, monitored by online MR temperature control. By using an effective combination of image guidance and energy delivery, MRgFUS therefore allows for preservation of uterine function while obviating the need for a minimally invasive procedure or surgery.Academic Radiology 10/2005; 12(9):1158-66. · 1.69 Impact Factor
[show abstract] [hide abstract]
ABSTRACT: The (1014) cleavage plane of calcite has been investigated by atomic force microscopy in water at room temperature. True lateral atomic-scale resolution was achieved; the atomic-scale periodicities as well as the expected relative positions of the atoms within each unit cell were obtained. Along monoatomic step lines, atomic-scale kinks, representing point-like defects, were resolved. Attractive forces on the order of 10(-11) newton acting between single atomic sites on the sample and the front atoms of the tip were directly measured and provided the highest, most reliable resolution on a flat, well-ordered surface.Science 07/1993; 260(5113):1451-6. · 31.20 Impact Factor